{"thread":{"id":"40994","subject":"[PATCH 2/8] xread: poll on non blocking fds","startedAt":"2015-12-14T19:37:10Z","lastAt":"2015-12-15T06:12:49Z","messageCount":30,"participants":["Stefan Beller","Johannes Sixt","Junio C Hamano","Eric Sunshine","Jeff King"],"isPatch":true,"patchVersion":1,"patchTotal":8},"messages":[{"id":"274403","messageId":"1450121838-7069-1-git-send-email-sbeller@google.com","threadId":"40994","inReplyTo":null,"subject":"[PATCH 0/8] Rerolling sb/submodule-parallel-fetch for the time after 2.7","fromName":"Stefan Beller","fromEmail":"sbeller@google.com","sentAt":"2015-12-14T19:37:10Z","receivedAt":"2015-12-14T19:37:10Z","isPatch":true,"sender":{"key":"stefanbeller@gmail.com","avatar":"https://avatars.githubusercontent.com/u/455868?v=4"},"body":"I am sending out a new version for replacing sb/submodule-parallel-fetch for\nthe time after the 2.7 release.\n\nThe content are \n * all patches as in the branch sb/submodule-parallel-fetch\n * inlcuding the fixups as suggested by Hannes, \n * write a message to the debug log for better testing and debugging purposes\n (a patch cherry picked from the series which is supposed to build on top of this)\n\nThe patches themselves were rebased such that there are no fixup commits\nany more, but we get things right the first time.\n\nThe commit message of \"run-command: add an asynchronous parallel child processor\"\nhas slightly been updated to mention the fact that we don't want to use waitpid(-1)\nbut rather use the assumption of child's stderr living as long as the child itself.\n\nThanks,\nStefan\n\n\nJonathan Nieder (1):\n submodule.c: write \"Fetching submodule \" to stderr\n\nStefan Beller (7):\n xread: poll on non blocking fds\n xread_nonblock: add functionality to read from fds without blocking\n strbuf: add strbuf_read_once to read without blocking\n sigchain: add command to pop all common signals\n run-command: add an asynchronous parallel child processor\n fetch_populated_submodules: use new parallel job processing\n submodules: allow parallel fetching, add tests and documentation\n\n Documentation/fetch-options.txt | 7 +\n builtin/fetch.c | 6 +-\n builtin/pull.c | 6 +\n git-compat-util.h | 1 +\n run-command.c | 335 ++++++++++++++++++++++++++++++++++++++++\n run-command.h | 80 ++++++++++\n sigchain.c | 9 ++\n sigchain.h | 1 +\n strbuf.c | 11 ++\n strbuf.h | 8 +\n submodule.c | 141 +++++++++++------\n submodule.h | 2 +-\n t/t0061-run-command.sh | 53 +++++++\n t/t5526-fetch-submodules.sh | 71 ++++++---\n test-run-command.c | 55 ++++++-\n wrapper.c | 35 ++++-\n 16 files changed, 747 insertions(+), 74 deletions(-)\n\n-- \n2.6.4.443.ge094245.dirty\n"},{"id":"274402","messageId":"1450121838-7069-2-git-send-email-sbeller@google.com","threadId":"40994","inReplyTo":"1450121838-7069-1-git-send-email-sbeller@google.com","subject":"[PATCH 1/8] submodule.c: write \"Fetching submodule \" to stderr","fromName":"Stefan Beller","fromEmail":"sbeller@google.com","sentAt":"2015-12-14T19:37:11Z","receivedAt":"2015-12-14T19:37:11Z","isPatch":true,"sender":{"key":"stefanbeller@gmail.com","avatar":"https://avatars.githubusercontent.com/u/455868?v=4"},"body":"From: Jonathan Nieder \n\nThe \"Pushing submodule \" progress output correctly goes to\nstderr, but \"Fetching submodule \" is going to stdout by\nmistake. Fix it to write to stderr.\n\nNoticed while trying to implement a parallel submodule fetch. When\nthis particular output line went to a different file descriptor, it\nwas buffered separately, resulting in wrongly interleaved output if\nwe copied it to the terminal naively.\n\nSigned-off-by: Jonathan Nieder \nSigned-off-by: Stefan Beller \nSigned-off-by: Junio C Hamano \n---\n submodule.c | 2 +-\n t/t5526-fetch-submodules.sh | 51 +++++++++++++++++++++++----------------------\n 2 files changed, 27 insertions(+), 26 deletions(-)\n\ndiff --git a/submodule.c b/submodule.c\nindex 14e7624..8386477 100644\n--- a/submodule.c\n+++ b/submodule.c\n@@ -689,7 +689,7 @@ int fetch_populated_submodules(const struct argv_array *options,\n \t\t\tgit_dir = submodule_git_dir.buf;\n \t\tif (is_directory(git_dir)) {\n \t\t\tif (!quiet)\n-\t\t\t\tprintf(\"Fetching submodule %s%s\\n\", prefix, ce->name);\n+\t\t\t\tfprintf(stderr, \"Fetching submodule %s%s\\n\", prefix, ce->name);\n \t\t\tcp.dir = submodule_path.buf;\n \t\t\targv_array_push(&argv, default_argv);\n \t\t\targv_array_push(&argv, \"--submodule-prefix\");\ndiff --git a/t/t5526-fetch-submodules.sh b/t/t5526-fetch-submodules.sh\nindex a4532b0..17759b14 100755\n--- a/t/t5526-fetch-submodules.sh\n+++ b/t/t5526-fetch-submodules.sh\n@@ -16,7 +16,8 @@ add_upstream_commit() {\n \t\tgit add subfile &&\n \t\tgit commit -m new subfile &&\n \t\thead2=$(git rev-parse --short HEAD) &&\n-\t\techo \"From $pwd/submodule\" > ../expect.err &&\n+\t\techo \"Fetching submodule submodule\" > ../expect.err &&\n+\t\techo \"From $pwd/submodule\" >> ../expect.err &&\n \t\techo \" $head1..$head2 master -> origin/master\" >> ../expect.err\n \t) &&\n \t(\n@@ -27,6 +28,7 @@ add_upstream_commit() {\n \t\tgit add deepsubfile &&\n \t\tgit commit -m new deepsubfile &&\n \t\thead2=$(git rev-parse --short HEAD) &&\n+\t\techo \"Fetching submodule submodule/subdir/deepsubmodule\" >> ../expect.err\n \t\techo \"From $pwd/deepsubmodule\" >> ../expect.err &&\n \t\techo \" $head1..$head2 master -> origin/master\" >> ../expect.err\n \t)\n@@ -56,9 +58,7 @@ test_expect_success setup '\n \t(\n \t\tcd downstream &&\n \t\tgit submodule update --init --recursive\n-\t) &&\n-\techo \"Fetching submodule submodule\" > expect.out &&\n-\techo \"Fetching submodule submodule/subdir/deepsubmodule\" >> expect.out\n+\t)\n '\n \n test_expect_success \"fetch --recurse-submodules recurses into submodules\" '\n@@ -67,7 +67,7 @@ test_expect_success \"fetch --recurse-submodules recurses into submodules\" '\n \t\tcd downstream &&\n \t\tgit fetch --recurse-submodules >../actual.out 2>../actual.err\n \t) &&\n-\ttest_i18ncmp expect.out actual.out &&\n+\ttest_must_be_empty actual.out &&\n \ttest_i18ncmp expect.err actual.err\n '\n \n@@ -96,7 +96,7 @@ test_expect_success \"using fetchRecurseSubmodules=true in .gitmodules recurses i\n \t\tgit config -f .gitmodules submodule.submodule.fetchRecurseSubmodules true &&\n \t\tgit fetch >../actual.out 2>../actual.err\n \t) &&\n-\ttest_i18ncmp expect.out actual.out &&\n+\ttest_must_be_empty actual.out &&\n \ttest_i18ncmp expect.err actual.err\n '\n \n@@ -127,7 +127,7 @@ test_expect_success \"--recurse-submodules overrides fetchRecurseSubmodules setti\n \t\tgit config --unset -f .gitmodules submodule.submodule.fetchRecurseSubmodules &&\n \t\tgit config --unset submodule.submodule.fetchRecurseSubmodules\n \t) &&\n-\ttest_i18ncmp expect.out actual.out &&\n+\ttest_must_be_empty actual.out &&\n \ttest_i18ncmp expect.err actual.err\n '\n \n@@ -146,7 +146,7 @@ test_expect_success \"--dry-run propagates to submodules\" '\n \t\tcd downstream &&\n \t\tgit fetch --recurse-submodules --dry-run >../actual.out 2>../actual.err\n \t) &&\n-\ttest_i18ncmp expect.out actual.out &&\n+\ttest_must_be_empty actual.out &&\n \ttest_i18ncmp expect.err actual.err\n '\n \n@@ -155,7 +155,7 @@ test_expect_success \"Without --dry-run propagates to submodules\" '\n \t\tcd downstream &&\n \t\tgit fetch --recurse-submodules >../actual.out 2>../actual.err\n \t) &&\n-\ttest_i18ncmp expect.out actual.out &&\n+\ttest_must_be_empty actual.out &&\n \ttest_i18ncmp expect.err actual.err\n '\n \n@@ -166,7 +166,7 @@ test_expect_success \"recurseSubmodules=true propagates into submodules\" '\n \t\tgit config fetch.recurseSubmodules true\n \t\tgit fetch >../actual.out 2>../actual.err\n \t) &&\n-\ttest_i18ncmp expect.out actual.out &&\n+\ttest_must_be_empty actual.out &&\n \ttest_i18ncmp expect.err actual.err\n '\n \n@@ -180,7 +180,7 @@ test_expect_success \"--recurse-submodules overrides config in submodule\" '\n \t\t) &&\n \t\tgit fetch --recurse-submodules >../actual.out 2>../actual.err\n \t) &&\n-\ttest_i18ncmp expect.out actual.out &&\n+\ttest_must_be_empty actual.out &&\n \ttest_i18ncmp expect.err actual.err\n '\n \n@@ -214,16 +214,15 @@ test_expect_success \"Recursion stops when no new submodule commits are fetched\"\n \tgit add submodule &&\n \tgit commit -m \"new submodule\" &&\n \thead2=$(git rev-parse --short HEAD) &&\n-\techo \"Fetching submodule submodule\" > expect.out.sub &&\n \techo \"From $pwd/.\" > expect.err.sub &&\n \techo \" $head1..$head2 master -> origin/master\" >>expect.err.sub &&\n-\thead -2 expect.err >> expect.err.sub &&\n+\thead -3 expect.err >> expect.err.sub &&\n \t(\n \t\tcd downstream &&\n \t\tgit fetch >../actual.out 2>../actual.err\n \t) &&\n \ttest_i18ncmp expect.err.sub actual.err &&\n-\ttest_i18ncmp expect.out.sub actual.out\n+\ttest_must_be_empty actual.out\n '\n \n test_expect_success \"Recursion doesn't happen when new superproject commits don't change any submodules\" '\n@@ -269,7 +268,7 @@ test_expect_success \"Recursion picks up config in submodule\" '\n \t\t)\n \t) &&\n \ttest_i18ncmp expect.err.sub actual.err &&\n-\ttest_i18ncmp expect.out actual.out\n+\ttest_must_be_empty actual.out\n '\n \n test_expect_success \"Recursion picks up all submodules when necessary\" '\n@@ -285,7 +284,8 @@ test_expect_success \"Recursion picks up all submodules when necessary\" '\n \t\tgit add subdir/deepsubmodule &&\n \t\tgit commit -m \"new deepsubmodule\"\n \t\thead2=$(git rev-parse --short HEAD) &&\n-\t\techo \"From $pwd/submodule\" > ../expect.err.sub &&\n+\t\techo \"Fetching submodule submodule\" > ../expect.err.sub &&\n+\t\techo \"From $pwd/submodule\" >> ../expect.err.sub &&\n \t\techo \" $head1..$head2 master -> origin/master\" >> ../expect.err.sub\n \t) &&\n \thead1=$(git rev-parse --short HEAD) &&\n@@ -295,13 +295,13 @@ test_expect_success \"Recursion picks up all submodules when necessary\" '\n \techo \"From $pwd/.\" > expect.err.2 &&\n \techo \" $head1..$head2 master -> origin/master\" >> expect.err.2 &&\n \tcat expect.err.sub >> expect.err.2 &&\n-\ttail -2 expect.err >> expect.err.2 &&\n+\ttail -3 expect.err >> expect.err.2 &&\n \t(\n \t\tcd downstream &&\n \t\tgit fetch >../actual.out 2>../actual.err\n \t) &&\n \ttest_i18ncmp expect.err.2 actual.err &&\n-\ttest_i18ncmp expect.out actual.out\n+\ttest_must_be_empty actual.out\n '\n \n test_expect_success \"'--recurse-submodules=on-demand' doesn't recurse when no new commits are fetched in the superproject (and ignores config)\" '\n@@ -317,7 +317,8 @@ test_expect_success \"'--recurse-submodules=on-demand' doesn't recurse when no ne\n \t\tgit add subdir/deepsubmodule &&\n \t\tgit commit -m \"new deepsubmodule\" &&\n \t\thead2=$(git rev-parse --short HEAD) &&\n-\t\techo \"From $pwd/submodule\" > ../expect.err.sub &&\n+\t\techo Fetching submodule submodule > ../expect.err.sub &&\n+\t\techo \"From $pwd/submodule\" >> ../expect.err.sub &&\n \t\techo \" $head1..$head2 master -> origin/master\" >> ../expect.err.sub\n \t) &&\n \t(\n@@ -335,7 +336,7 @@ test_expect_success \"'--recurse-submodules=on-demand' recurses as deep as necess\n \tgit add submodule &&\n \tgit commit -m \"new submodule\" &&\n \thead2=$(git rev-parse --short HEAD) &&\n-\ttail -2 expect.err > expect.err.deepsub &&\n+\ttail -3 expect.err > expect.err.deepsub &&\n \techo \"From $pwd/.\" > expect.err &&\n \techo \" $head1..$head2 master -> origin/master\" >>expect.err &&\n \tcat expect.err.sub >> expect.err &&\n@@ -354,7 +355,7 @@ test_expect_success \"'--recurse-submodules=on-demand' recurses as deep as necess\n \t\t\tgit config --unset -f .gitmodules submodule.subdir/deepsubmodule.fetchRecursive\n \t\t)\n \t) &&\n-\ttest_i18ncmp expect.out actual.out &&\n+\ttest_must_be_empty actual.out &&\n \ttest_i18ncmp expect.err actual.err\n '\n \n@@ -388,7 +389,7 @@ test_expect_success \"'fetch.recurseSubmodules=on-demand' overrides global config\n \thead2=$(git rev-parse --short HEAD) &&\n \techo \"From $pwd/.\" > expect.err.2 &&\n \techo \" $head1..$head2 master -> origin/master\" >>expect.err.2 &&\n-\thead -2 expect.err >> expect.err.2 &&\n+\thead -3 expect.err >> expect.err.2 &&\n \t(\n \t\tcd downstream &&\n \t\tgit config fetch.recurseSubmodules on-demand &&\n@@ -399,7 +400,7 @@ test_expect_success \"'fetch.recurseSubmodules=on-demand' overrides global config\n \t\tcd downstream &&\n \t\tgit config --unset fetch.recurseSubmodules\n \t) &&\n-\ttest_i18ncmp expect.out.sub actual.out &&\n+\ttest_must_be_empty actual.out &&\n \ttest_i18ncmp expect.err.2 actual.err\n '\n \n@@ -416,7 +417,7 @@ test_expect_success \"'submodule..fetchRecurseSubmodules=on-demand' override\n \thead2=$(git rev-parse --short HEAD) &&\n \techo \"From $pwd/.\" > expect.err.2 &&\n \techo \" $head1..$head2 master -> origin/master\" >>expect.err.2 &&\n-\thead -2 expect.err >> expect.err.2 &&\n+\thead -3 expect.err >> expect.err.2 &&\n \t(\n \t\tcd downstream &&\n \t\tgit config submodule.submodule.fetchRecurseSubmodules on-demand &&\n@@ -427,7 +428,7 @@ test_expect_success \"'submodule..fetchRecurseSubmodules=on-demand' override\n \t\tcd downstream &&\n \t\tgit config --unset submodule.submodule.fetchRecurseSubmodules\n \t) &&\n-\ttest_i18ncmp expect.out.sub actual.out &&\n+\ttest_must_be_empty actual.out &&\n \ttest_i18ncmp expect.err.2 actual.err\n '\n \n-- \n2.6.4.443.ge094245.dirty\n"},{"id":"274401","messageId":"1450121838-7069-3-git-send-email-sbeller@google.com","threadId":"40994","inReplyTo":"1450121838-7069-1-git-send-email-sbeller@google.com","subject":"[PATCH 2/8] xread: poll on non blocking fds","fromName":"Stefan Beller","fromEmail":"sbeller@google.com","sentAt":"2015-12-14T19:37:12Z","receivedAt":"2015-12-14T19:37:12Z","isPatch":true,"sender":{"key":"stefanbeller@gmail.com","avatar":"https://avatars.githubusercontent.com/u/455868?v=4"},"body":">From the man page:\nEAGAIN The file descriptor fd refers to a file other than a socket\n and has been marked nonblocking (O_NONBLOCK), and the read\n would block.\n\nEAGAIN or EWOULDBLOCK\n The file descriptor fd refers to a socket and has been marked\n nonblocking (O_NONBLOCK), and the read would block. POSIX.1-2001\n allows either error to be returned for this case, and does not\n require these constants to have the same value, so a portable\n application should check for both possibilities.\n\nIf we get an EAGAIN or EWOULDBLOCK the fd must have set O_NONBLOCK.\nAs the intent of xread is to read as much as possible either until the\nfd is EOF or an actual error occurs, we can ease the feeder of the fd\nby not spinning the whole time, but rather wait for it politely by not\nbusy waiting.\n\nWe should not care if the call to poll failed, as we're in an infinite\nloop and can only get out with the correct read().\n\nSigned-off-by: Stefan Beller \nSigned-off-by: Junio C Hamano \n---\n wrapper.c | 13 +++++++++++--\n 1 file changed, 11 insertions(+), 2 deletions(-)\n\ndiff --git a/wrapper.c b/wrapper.c\nindex 6fcaa4d..4f720fe 100644\n--- a/wrapper.c\n+++ b/wrapper.c\n@@ -236,8 +236,17 @@ ssize_t xread(int fd, void *buf, size_t len)\n \t len = MAX_IO_SIZE;\n \twhile (1) {\n \t\tnr = read(fd, buf, len);\n-\t\tif ((nr < 0) && (errno == EAGAIN || errno == EINTR))\n-\t\t\tcontinue;\n+\t\tif (nr < 0) {\n+\t\t\tif (errno == EINTR)\n+\t\t\t\tcontinue;\n+\t\t\tif (errno == EAGAIN || errno == EWOULDBLOCK) {\n+\t\t\t\tstruct pollfd pfd;\n+\t\t\t\tpfd.events = POLLIN;\n+\t\t\t\tpfd.fd = fd;\n+\t\t\t\t/* We deliberately ignore the return value */\n+\t\t\t\tpoll(&pfd, 1, -1);\n+\t\t\t}\n+\t\t}\n \t\treturn nr;\n \t}\n }\n-- \n2.6.4.443.ge094245.dirty\n"},{"id":"274406","messageId":"1450121838-7069-4-git-send-email-sbeller@google.com","threadId":"40994","inReplyTo":"1450121838-7069-1-git-send-email-sbeller@google.com","subject":"[PATCH 3/8] xread_nonblock: add functionality to read from fds without blocking","fromName":"Stefan Beller","fromEmail":"sbeller@google.com","sentAt":"2015-12-14T19:37:13Z","receivedAt":"2015-12-14T19:37:13Z","isPatch":true,"sender":{"key":"stefanbeller@gmail.com","avatar":"https://avatars.githubusercontent.com/u/455868?v=4"},"body":"Provide a wrapper to read(), similar to xread(), that restarts on\nEINTR but not EAGAIN (or EWOULDBLOCK). This enables the caller to\nhandle polling itself, possibly polling multiple sockets or performing\nsome other action.\n\nHelped-by: Jacob Keller \nHelped-by: Jeff King ,\nHelped-by: Junio C Hamano \nSigned-off-by: Stefan Beller \nSigned-off-by: Junio C Hamano \n---\n git-compat-util.h | 1 +\n wrapper.c | 22 ++++++++++++++++++++++\n 2 files changed, 23 insertions(+)\n\ndiff --git a/git-compat-util.h b/git-compat-util.h\nindex 8e39867..87456a3 100644\n--- a/git-compat-util.h\n+++ b/git-compat-util.h\n@@ -723,6 +723,7 @@ extern void *xmmap(void *start, size_t length, int prot, int flags, int fd, off_\n extern void *xmmap_gently(void *start, size_t length, int prot, int flags, int fd, off_t offset);\n extern int xopen(const char *path, int flags, ...);\n extern ssize_t xread(int fd, void *buf, size_t len);\n+extern ssize_t xread_nonblock(int fd, void *buf, size_t len);\n extern ssize_t xwrite(int fd, const void *buf, size_t len);\n extern ssize_t xpread(int fd, void *buf, size_t len, off_t offset);\n extern int xdup(int fd);\ndiff --git a/wrapper.c b/wrapper.c\nindex 4f720fe..f71237c 100644\n--- a/wrapper.c\n+++ b/wrapper.c\n@@ -252,6 +252,28 @@ ssize_t xread(int fd, void *buf, size_t len)\n }\n \n /*\n+ * xread_nonblock() is the same a read(), but it automatically restarts read()\n+ * interrupted operations (EINTR). xread_nonblock() DOES NOT GUARANTEE that\n+ * \"len\" bytes is read. EWOULDBLOCK is turned into EAGAIN.\n+ */\n+ssize_t xread_nonblock(int fd, void *buf, size_t len)\n+{\n+\tssize_t nr;\n+\tif (len > MAX_IO_SIZE)\n+\t\tlen = MAX_IO_SIZE;\n+\twhile (1) {\n+\t\tnr = read(fd, buf, len);\n+\t\tif (nr < 0) {\n+\t\t\tif (errno == EINTR)\n+\t\t\t\tcontinue;\n+\t\t\tif (errno == EWOULDBLOCK)\n+\t\t\t\terrno = EAGAIN;\n+\t\t}\n+\t\treturn nr;\n+\t}\n+}\n+\n+/*\n * xwrite() is the same a write(), but it automatically restarts write()\n * operations with a recoverable error (EAGAIN and EINTR). xwrite() DOES NOT\n * GUARANTEE that \"len\" bytes is written even if the operation is successful.\n-- \n2.6.4.443.ge094245.dirty\n"},{"id":"274405","messageId":"1450121838-7069-5-git-send-email-sbeller@google.com","threadId":"40994","inReplyTo":"1450121838-7069-1-git-send-email-sbeller@google.com","subject":"[PATCH 4/8] strbuf: add strbuf_read_once to read without blocking","fromName":"Stefan Beller","fromEmail":"sbeller@google.com","sentAt":"2015-12-14T19:37:14Z","receivedAt":"2015-12-14T19:37:14Z","isPatch":true,"sender":{"key":"stefanbeller@gmail.com","avatar":"https://avatars.githubusercontent.com/u/455868?v=4"},"body":"The new call will read from a file descriptor into a strbuf once. The\nunderlying call xread_nonblock is meant to execute without blocking if\nthe file descriptor is set to O_NONBLOCK. It is a bug to call\nstrbuf_read_once on a file descriptor which would block.\n\nSigned-off-by: Stefan Beller \nSigned-off-by: Junio C Hamano \n---\n strbuf.c | 11 +++++++++++\n strbuf.h | 8 ++++++++\n 2 files changed, 19 insertions(+)\n\ndiff --git a/strbuf.c b/strbuf.c\nindex d76f0ae..b552a13 100644\n--- a/strbuf.c\n+++ b/strbuf.c\n@@ -384,6 +384,17 @@ ssize_t strbuf_read(struct strbuf *sb, int fd, size_t hint)\n \treturn sb->len - oldlen;\n }\n \n+ssize_t strbuf_read_once(struct strbuf *sb, int fd, size_t hint)\n+{\n+\tssize_t cnt;\n+\n+\tstrbuf_grow(sb, hint ? hint : 8192);\n+\tcnt = xread_nonblock(fd, sb->buf + sb->len, sb->alloc - sb->len - 1);\n+\tif (cnt > 0)\n+\t\tstrbuf_setlen(sb, sb->len + cnt);\n+\treturn cnt;\n+}\n+\n #define STRBUF_MAXLINK (2*PATH_MAX)\n \n int strbuf_readlink(struct strbuf *sb, const char *path, size_t hint)\ndiff --git a/strbuf.h b/strbuf.h\nindex 7123fca..c3e5980 100644\n--- a/strbuf.h\n+++ b/strbuf.h\n@@ -367,6 +367,14 @@ extern size_t strbuf_fread(struct strbuf *, size_t, FILE *);\n extern ssize_t strbuf_read(struct strbuf *, int fd, size_t hint);\n \n /**\n+ * Returns the number of new bytes appended to the sb.\n+ * Negative return value signals there was an error returned from\n+ * underlying read(2), in which case the caller should check errno.\n+ * e.g. errno == EAGAIN when the read may have blocked.\n+ */\n+extern ssize_t strbuf_read_once(struct strbuf *, int fd, size_t hint);\n+\n+/**\n * Read the contents of a file, specified by its path. The third argument\n * can be used to give a hint about the file size, to avoid reallocs.\n */\n-- \n2.6.4.443.ge094245.dirty\n"},{"id":"274407","messageId":"1450121838-7069-6-git-send-email-sbeller@google.com","threadId":"40994","inReplyTo":"1450121838-7069-1-git-send-email-sbeller@google.com","subject":"[PATCH 5/8] sigchain: add command to pop all common signals","fromName":"Stefan Beller","fromEmail":"sbeller@google.com","sentAt":"2015-12-14T19:37:15Z","receivedAt":"2015-12-14T19:37:15Z","isPatch":true,"sender":{"key":"stefanbeller@gmail.com","avatar":"https://avatars.githubusercontent.com/u/455868?v=4"},"body":"The new method removes all common signal handlers that were installed\nby sigchain_push.\n\nCC: Jeff King \nSigned-off-by: Stefan Beller \nSigned-off-by: Junio C Hamano \n---\n sigchain.c | 9 +++++++++\n sigchain.h | 1 +\n 2 files changed, 10 insertions(+)\n\ndiff --git a/sigchain.c b/sigchain.c\nindex faa375d..2ac43bb 100644\n--- a/sigchain.c\n+++ b/sigchain.c\n@@ -50,3 +50,12 @@ void sigchain_push_common(sigchain_fun f)\n \tsigchain_push(SIGQUIT, f);\n \tsigchain_push(SIGPIPE, f);\n }\n+\n+void sigchain_pop_common(void)\n+{\n+\tsigchain_pop(SIGPIPE);\n+\tsigchain_pop(SIGQUIT);\n+\tsigchain_pop(SIGTERM);\n+\tsigchain_pop(SIGHUP);\n+\tsigchain_pop(SIGINT);\n+}\ndiff --git a/sigchain.h b/sigchain.h\nindex 618083b..138b20f 100644\n--- a/sigchain.h\n+++ b/sigchain.h\n@@ -7,5 +7,6 @@ int sigchain_push(int sig, sigchain_fun f);\n int sigchain_pop(int sig);\n \n void sigchain_push_common(sigchain_fun f);\n+void sigchain_pop_common(void);\n \n #endif /* SIGCHAIN_H */\n-- \n2.6.4.443.ge094245.dirty\n"},{"id":"274404","messageId":"1450121838-7069-7-git-send-email-sbeller@google.com","threadId":"40994","inReplyTo":"1450121838-7069-1-git-send-email-sbeller@google.com","subject":"[PATCH 6/8] run-command: add an asynchronous parallel child processor","fromName":"Stefan Beller","fromEmail":"sbeller@google.com","sentAt":"2015-12-14T19:37:16Z","receivedAt":"2015-12-14T19:37:16Z","isPatch":true,"sender":{"key":"stefanbeller@gmail.com","avatar":"https://avatars.githubusercontent.com/u/455868?v=4"},"body":"This allows to run external commands in parallel with ordered output\non stderr.\n\nIf we run external commands in parallel we cannot pipe the output directly\nto the our stdout/err as it would mix up. So each process's output will\nflow through a pipe, which we buffer. One subprocess can be directly\npiped to out stdout/err for a low latency feedback to the user.\n\nExample:\nLet's assume we have 5 submodules A,B,C,D,E and each fetch takes a\ndifferent amount of time as the different submodules vary in size, then\nthe output of fetches in sequential order might look like this:\n\n time -->\n output: |---A---| |-B-| |-------C-------| |-D-| |-E-|\n\nWhen we schedule these submodules into maximal two parallel processes,\na schedule and sample output over time may look like this:\n\nprocess 1: |---A---| |-D-| |-E-|\n\nprocess 2: |-B-| |-------C-------|\n\noutput: |---A---|B|---C-------|DE\n\nSo A will be perceived as it would run normally in the single child\nversion. As B has finished by the time A is done, we can dump its whole\nprogress buffer on stderr, such that it looks like it finished in no\ntime. Once that is done, C is determined to be the visible child and\nits progress will be reported in real time.\n\nSo this way of output is really good for human consumption, as it only\nchanges the timing, not the actual output.\n\nFor machine consumption the output needs to be prepared in the tasks,\nby either having a prefix per line or per block to indicate whose tasks\noutput is displayed, because the output order may not follow the\noriginal sequential ordering:\n\n |----A----| |--B--| |-C-|\n\nwill be scheduled to be all parallel:\n\nprocess 1: |----A----|\nprocess 2: |--B--|\nprocess 3: |-C-|\noutput: |----A----|CB\n\nThis happens because C finished before B did, so it will be queued for\noutput before B.\n\nThe detection when a child has finished executing is done the same way as\ntwo fold. First we check regularly if the stderr pipe still exists in an\ninterleaved manner with other actions such as checking other children\nfor their liveliness or starting new children. Once a child closed their\nstderr stream, we assume it is stopping very soon, such that we can use\nthe `finish_command` code borrowed from the single external process\nexecution interface.\n\nBy maintaining the strong assumption of stderr being open until the\nvery end of a child process, we can avoid other hassle such as an\nimplementation using `waitpid(-1)`, which is not implemented in Windows.\n\nSigned-off-by: Stefan Beller \n---\n run-command.c | 335 +++++++++++++++++++++++++++++++++++++++++++++++++\n run-command.h | 80 ++++++++++++\n t/t0061-run-command.sh | 53 ++++++++\n test-run-command.c | 55 +++++++-\n 4 files changed, 522 insertions(+), 1 deletion(-)\n\ndiff --git a/run-command.c b/run-command.c\nindex 13fa452..51fd72c 100644\n--- a/run-command.c\n+++ b/run-command.c\n@@ -3,6 +3,8 @@\n #include \"exec_cmd.h\"\n #include \"sigchain.h\"\n #include \"argv-array.h\"\n+#include \"thread-utils.h\"\n+#include \"strbuf.h\"\n \n void child_process_init(struct child_process *child)\n {\n@@ -865,3 +867,336 @@ int capture_command(struct child_process *cmd, struct strbuf *buf, size_t hint)\n \tclose(cmd->out);\n \treturn finish_command(cmd);\n }\n+\n+enum child_state {\n+\tGIT_CP_FREE,\n+\tGIT_CP_WORKING,\n+\tGIT_CP_WAIT_CLEANUP,\n+};\n+\n+struct parallel_processes {\n+\tvoid *data;\n+\n+\tint max_processes;\n+\tint nr_processes;\n+\n+\tget_next_task_fn get_next_task;\n+\tstart_failure_fn start_failure;\n+\ttask_finished_fn task_finished;\n+\n+\tstruct {\n+\t\tenum child_state state;\n+\t\tstruct child_process process;\n+\t\tstruct strbuf err;\n+\t\tvoid *data;\n+\t} *children;\n+\t/*\n+\t * The struct pollfd is logically part of *children,\n+\t * but the system call expects it as its own array.\n+\t */\n+\tstruct pollfd *pfd;\n+\n+\tunsigned shutdown : 1;\n+\n+\tint output_owner;\n+\tstruct strbuf buffered_output; /* of finished children */\n+};\n+\n+static int default_start_failure(struct child_process *cp,\n+\t\t\t\t struct strbuf *err,\n+\t\t\t\t void *pp_cb,\n+\t\t\t\t void *pp_task_cb)\n+{\n+\tint i;\n+\n+\tstrbuf_addstr(err, \"Starting a child failed:\");\n+\tfor (i = 0; cp->argv[i]; i++)\n+\t\tstrbuf_addf(err, \" %s\", cp->argv[i]);\n+\n+\treturn 0;\n+}\n+\n+static int default_task_finished(int result,\n+\t\t\t\t struct child_process *cp,\n+\t\t\t\t struct strbuf *err,\n+\t\t\t\t void *pp_cb,\n+\t\t\t\t void *pp_task_cb)\n+{\n+\tint i;\n+\n+\tif (!result)\n+\t\treturn 0;\n+\n+\tstrbuf_addf(err, \"A child failed with return code %d:\", result);\n+\tfor (i = 0; cp->argv[i]; i++)\n+\t\tstrbuf_addf(err, \" %s\", cp->argv[i]);\n+\n+\treturn 0;\n+}\n+\n+static void kill_children(struct parallel_processes *pp, int signo)\n+{\n+\tint i, n = pp->max_processes;\n+\n+\tfor (i = 0; i < n; i++)\n+\t\tif (pp->children[i].state == GIT_CP_WORKING)\n+\t\t\tkill(pp->children[i].process.pid, signo);\n+}\n+\n+static struct parallel_processes *pp_for_signal;\n+\n+static void handle_children_on_signal(int signo)\n+{\n+\tkill_children(pp_for_signal, signo);\n+\tsigchain_pop(signo);\n+\traise(signo);\n+}\n+\n+static void pp_init(struct parallel_processes *pp,\n+\t\t int n,\n+\t\t get_next_task_fn get_next_task,\n+\t\t start_failure_fn start_failure,\n+\t\t task_finished_fn task_finished,\n+\t\t void *data)\n+{\n+\tint i;\n+\n+\tif (n < 1)\n+\t\tn = online_cpus();\n+\n+\tpp->max_processes = n;\n+\n+\ttrace_printf(\"run_processes_parallel: preparing to run up to %d tasks\", n);\n+\n+\tpp->data = data;\n+\tif (!get_next_task)\n+\t\tdie(\"BUG: you need to specify a get_next_task function\");\n+\tpp->get_next_task = get_next_task;\n+\n+\tpp->start_failure = start_failure ? start_failure : default_start_failure;\n+\tpp->task_finished = task_finished ? task_finished : default_task_finished;\n+\n+\tpp->nr_processes = 0;\n+\tpp->output_owner = 0;\n+\tpp->shutdown = 0;\n+\tpp->children = xcalloc(n, sizeof(*pp->children));\n+\tpp->pfd = xcalloc(n, sizeof(*pp->pfd));\n+\tstrbuf_init(&pp->buffered_output, 0);\n+\n+\tfor (i = 0; i < n; i++) {\n+\t\tstrbuf_init(&pp->children[i].err, 0);\n+\t\tchild_process_init(&pp->children[i].process);\n+\t\tpp->pfd[i].events = POLLIN | POLLHUP;\n+\t\tpp->pfd[i].fd = -1;\n+\t}\n+\n+\tpp_for_signal = pp;\n+\tsigchain_push_common(handle_children_on_signal);\n+}\n+\n+static void pp_cleanup(struct parallel_processes *pp)\n+{\n+\tint i;\n+\n+\ttrace_printf(\"run_processes_parallel: done\");\n+\tfor (i = 0; i < pp->max_processes; i++) {\n+\t\tstrbuf_release(&pp->children[i].err);\n+\t\tchild_process_clear(&pp->children[i].process);\n+\t}\n+\n+\tfree(pp->children);\n+\tfree(pp->pfd);\n+\n+\t/*\n+\t * When get_next_task added messages to the buffer in its last\n+\t * iteration, the buffered output is non empty.\n+\t */\n+\tfputs(pp->buffered_output.buf, stderr);\n+\tstrbuf_release(&pp->buffered_output);\n+\n+\tsigchain_pop_common();\n+}\n+\n+/* returns\n+ * 0 if a new task was started.\n+ * 1 if no new jobs was started (get_next_task ran out of work, non critical\n+ * problem with starting a new command)\n+ * <0 no new job was started, user wishes to shutdown early. Use negative code\n+ * to signal the children.\n+ */\n+static int pp_start_one(struct parallel_processes *pp)\n+{\n+\tint i, code;\n+\n+\tfor (i = 0; i < pp->max_processes; i++)\n+\t\tif (pp->children[i].state == GIT_CP_FREE)\n+\t\t\tbreak;\n+\tif (i == pp->max_processes)\n+\t\tdie(\"BUG: bookkeeping is hard\");\n+\n+\tcode = pp->get_next_task(&pp->children[i].process,\n+\t\t\t\t &pp->children[i].err,\n+\t\t\t\t pp->data,\n+\t\t\t\t &pp->children[i].data);\n+\tif (!code) {\n+\t\tstrbuf_addbuf(&pp->buffered_output, &pp->children[i].err);\n+\t\tstrbuf_reset(&pp->children[i].err);\n+\t\treturn 1;\n+\t}\n+\tpp->children[i].process.err = -1;\n+\tpp->children[i].process.stdout_to_stderr = 1;\n+\tpp->children[i].process.no_stdin = 1;\n+\n+\tif (start_command(&pp->children[i].process)) {\n+\t\tcode = pp->start_failure(&pp->children[i].process,\n+\t\t\t\t\t &pp->children[i].err,\n+\t\t\t\t\t pp->data,\n+\t\t\t\t\t &pp->children[i].data);\n+\t\tstrbuf_addbuf(&pp->buffered_output, &pp->children[i].err);\n+\t\tstrbuf_reset(&pp->children[i].err);\n+\t\tif (code)\n+\t\t\tpp->shutdown = 1;\n+\t\treturn code;\n+\t}\n+\n+\tpp->nr_processes++;\n+\tpp->children[i].state = GIT_CP_WORKING;\n+\tpp->pfd[i].fd = pp->children[i].process.err;\n+\treturn 0;\n+}\n+\n+static void pp_buffer_stderr(struct parallel_processes *pp, int output_timeout)\n+{\n+\tint i;\n+\n+\twhile ((i = poll(pp->pfd, pp->max_processes, output_timeout)) < 0) {\n+\t\tif (errno == EINTR)\n+\t\t\tcontinue;\n+\t\tpp_cleanup(pp);\n+\t\tdie_errno(\"poll\");\n+\t}\n+\n+\t/* Buffer output from all pipes. */\n+\tfor (i = 0; i < pp->max_processes; i++) {\n+\t\tif (pp->children[i].state == GIT_CP_WORKING &&\n+\t\t pp->pfd[i].revents & (POLLIN | POLLHUP)) {\n+\t\t\tint n = strbuf_read_once(&pp->children[i].err,\n+\t\t\t\t\t\t pp->children[i].process.err, 0);\n+\t\t\tif (n == 0) {\n+\t\t\t\tclose(pp->children[i].process.err);\n+\t\t\t\tpp->children[i].state = GIT_CP_WAIT_CLEANUP;\n+\t\t\t} else if (n < 0)\n+\t\t\t\tif (errno != EAGAIN)\n+\t\t\t\t\tdie_errno(\"read\");\n+\t\t}\n+\t}\n+}\n+\n+static void pp_output(struct parallel_processes *pp)\n+{\n+\tint i = pp->output_owner;\n+\tif (pp->children[i].state == GIT_CP_WORKING &&\n+\t pp->children[i].err.len) {\n+\t\tfputs(pp->children[i].err.buf, stderr);\n+\t\tstrbuf_reset(&pp->children[i].err);\n+\t}\n+}\n+\n+static int pp_collect_finished(struct parallel_processes *pp)\n+{\n+\tint i, code;\n+\tint n = pp->max_processes;\n+\tint result = 0;\n+\n+\twhile (pp->nr_processes > 0) {\n+\t\tfor (i = 0; i < pp->max_processes; i++)\n+\t\t\tif (pp->children[i].state == GIT_CP_WAIT_CLEANUP)\n+\t\t\t\tbreak;\n+\t\tif (i == pp->max_processes)\n+\t\t\tbreak;\n+\n+\t\tcode = finish_command(&pp->children[i].process);\n+\n+\t\tcode = pp->task_finished(code, &pp->children[i].process,\n+\t\t\t\t\t &pp->children[i].err, pp->data,\n+\t\t\t\t\t &pp->children[i].data);\n+\n+\t\tif (code)\n+\t\t\tresult = code;\n+\t\tif (code < 0)\n+\t\t\tbreak;\n+\n+\t\tpp->nr_processes--;\n+\t\tpp->children[i].state = GIT_CP_FREE;\n+\t\tpp->pfd[i].fd = -1;\n+\t\tchild_process_init(&pp->children[i].process);\n+\n+\t\tif (i != pp->output_owner) {\n+\t\t\tstrbuf_addbuf(&pp->buffered_output, &pp->children[i].err);\n+\t\t\tstrbuf_reset(&pp->children[i].err);\n+\t\t} else {\n+\t\t\tfputs(pp->children[i].err.buf, stderr);\n+\t\t\tstrbuf_reset(&pp->children[i].err);\n+\n+\t\t\t/* Output all other finished child processes */\n+\t\t\tfputs(pp->buffered_output.buf, stderr);\n+\t\t\tstrbuf_reset(&pp->buffered_output);\n+\n+\t\t\t/*\n+\t\t\t * Pick next process to output live.\n+\t\t\t * NEEDSWORK:\n+\t\t\t * For now we pick it randomly by doing a round\n+\t\t\t * robin. Later we may want to pick the one with\n+\t\t\t * the most output or the longest or shortest\n+\t\t\t * running process time.\n+\t\t\t */\n+\t\t\tfor (i = 0; i < n; i++)\n+\t\t\t\tif (pp->children[(pp->output_owner + i) % n].state == GIT_CP_WORKING)\n+\t\t\t\t\tbreak;\n+\t\t\tpp->output_owner = (pp->output_owner + i) % n;\n+\t\t}\n+\t}\n+\treturn result;\n+}\n+\n+int run_processes_parallel(int n,\n+\t\t\t get_next_task_fn get_next_task,\n+\t\t\t start_failure_fn start_failure,\n+\t\t\t task_finished_fn task_finished,\n+\t\t\t void *pp_cb)\n+{\n+\tint i, code;\n+\tint output_timeout = 100;\n+\tint spawn_cap = 4;\n+\tstruct parallel_processes pp;\n+\n+\tpp_init(&pp, n, get_next_task, start_failure, task_finished, pp_cb);\n+\twhile (1) {\n+\t\tfor (i = 0;\n+\t\t i < spawn_cap && !pp.shutdown &&\n+\t\t pp.nr_processes < pp.max_processes;\n+\t\t i++) {\n+\t\t\tcode = pp_start_one(&pp);\n+\t\t\tif (!code)\n+\t\t\t\tcontinue;\n+\t\t\tif (code < 0) {\n+\t\t\t\tpp.shutdown = 1;\n+\t\t\t\tkill_children(&pp, -code);\n+\t\t\t}\n+\t\t\tbreak;\n+\t\t}\n+\t\tif (!pp.nr_processes)\n+\t\t\tbreak;\n+\t\tpp_buffer_stderr(&pp, output_timeout);\n+\t\tpp_output(&pp);\n+\t\tcode = pp_collect_finished(&pp);\n+\t\tif (code) {\n+\t\t\tpp.shutdown = 1;\n+\t\t\tif (code < 0)\n+\t\t\t\tkill_children(&pp, -code);\n+\t\t}\n+\t}\n+\n+\tpp_cleanup(&pp);\n+\treturn 0;\n+}\ndiff --git a/run-command.h b/run-command.h\nindex 12bb26c..d5a57f9 100644\n--- a/run-command.h\n+++ b/run-command.h\n@@ -122,4 +122,84 @@ int start_async(struct async *async);\n int finish_async(struct async *async);\n int in_async(void);\n \n+/**\n+ * This callback should initialize the child process and preload the\n+ * error channel if desired. The preloading of is useful if you want to\n+ * have a message printed directly before the output of the child process.\n+ * pp_cb is the callback cookie as passed to run_processes_parallel.\n+ * You can store a child process specific callback cookie in pp_task_cb.\n+ *\n+ * Even after returning 0 to indicate that there are no more processes,\n+ * this function will be called again until there are no more running\n+ * child processes.\n+ *\n+ * Return 1 if the next child is ready to run.\n+ * Return 0 if there are currently no more tasks to be processed.\n+ * To send a signal to other child processes for abortion,\n+ * return the negative signal number.\n+ */\n+typedef int (*get_next_task_fn)(struct child_process *cp,\n+\t\t\t\tstruct strbuf *err,\n+\t\t\t\tvoid *pp_cb,\n+\t\t\t\tvoid **pp_task_cb);\n+\n+/**\n+ * This callback is called whenever there are problems starting\n+ * a new process.\n+ *\n+ * You must not write to stdout or stderr in this function. Add your\n+ * message to the strbuf err instead, which will be printed without\n+ * messing up the output of the other parallel processes.\n+ *\n+ * pp_cb is the callback cookie as passed into run_processes_parallel,\n+ * pp_task_cb is the callback cookie as passed into get_next_task_fn.\n+ *\n+ * Return 0 to continue the parallel processing. To abort return non zero.\n+ * To send a signal to other child processes for abortion, return\n+ * the negative signal number.\n+ */\n+typedef int (*start_failure_fn)(struct child_process *cp,\n+\t\t\t\tstruct strbuf *err,\n+\t\t\t\tvoid *pp_cb,\n+\t\t\t\tvoid *pp_task_cb);\n+\n+/**\n+ * This callback is called on every child process that finished processing.\n+ *\n+ * You must not write to stdout or stderr in this function. Add your\n+ * message to the strbuf err instead, which will be printed without\n+ * messing up the output of the other parallel processes.\n+ *\n+ * pp_cb is the callback cookie as passed into run_processes_parallel,\n+ * pp_task_cb is the callback cookie as passed into get_next_task_fn.\n+ *\n+ * Return 0 to continue the parallel processing. To abort return non zero.\n+ * To send a signal to other child processes for abortion, return\n+ * the negative signal number.\n+ */\n+typedef int (*task_finished_fn)(int result,\n+\t\t\t\tstruct child_process *cp,\n+\t\t\t\tstruct strbuf *err,\n+\t\t\t\tvoid *pp_cb,\n+\t\t\t\tvoid *pp_task_cb);\n+\n+/**\n+ * Runs up to n processes at the same time. Whenever a process can be\n+ * started, the callback get_next_task_fn is called to obtain the data\n+ * required to start another child process.\n+ *\n+ * The children started via this function run in parallel. Their output\n+ * (both stdout and stderr) is routed to stderr in a manner that output\n+ * from different tasks does not interleave.\n+ *\n+ * If start_failure_fn or task_finished_fn are NULL, default handlers\n+ * will be used. The default handlers will print an error message on\n+ * error without issuing an emergency stop.\n+ */\n+int run_processes_parallel(int n,\n+\t\t\t get_next_task_fn,\n+\t\t\t start_failure_fn,\n+\t\t\t task_finished_fn,\n+\t\t\t void *pp_cb);\n+\n #endif\ndiff --git a/t/t0061-run-command.sh b/t/t0061-run-command.sh\nindex 9acf628..12228b4 100755\n--- a/t/t0061-run-command.sh\n+++ b/t/t0061-run-command.sh\n@@ -47,4 +47,57 @@ test_expect_success POSIXPERM,SANITY 'unreadable directory in PATH' '\n \ttest_cmp expect actual\n '\n \n+cat >expect <<-EOF\n+preloaded output of a child\n+Hello\n+World\n+preloaded output of a child\n+Hello\n+World\n+preloaded output of a child\n+Hello\n+World\n+preloaded output of a child\n+Hello\n+World\n+EOF\n+\n+test_expect_success 'run_command runs in parallel with more jobs available than tasks' '\n+\ttest-run-command run-command-parallel 5 sh -c \"printf \\\"%s\\n%s\\n\\\" Hello World\" 2>actual &&\n+\ttest_cmp expect actual\n+'\n+\n+test_expect_success 'run_command runs in parallel with as many jobs as tasks' '\n+\ttest-run-command run-command-parallel 4 sh -c \"printf \\\"%s\\n%s\\n\\\" Hello World\" 2>actual &&\n+\ttest_cmp expect actual\n+'\n+\n+test_expect_success 'run_command runs in parallel with more tasks than jobs available' '\n+\ttest-run-command run-command-parallel 3 sh -c \"printf \\\"%s\\n%s\\n\\\" Hello World\" 2>actual &&\n+\ttest_cmp expect actual\n+'\n+\n+cat >expect <<-EOF\n+preloaded output of a child\n+asking for a quick stop\n+preloaded output of a child\n+asking for a quick stop\n+preloaded output of a child\n+asking for a quick stop\n+EOF\n+\n+test_expect_success 'run_command is asked to abort gracefully' '\n+\ttest-run-command run-command-abort 3 false 2>actual &&\n+\ttest_cmp expect actual\n+'\n+\n+cat >expect <<-EOF\n+no further jobs available\n+EOF\n+\n+test_expect_success 'run_command outputs ' '\n+\ttest-run-command run-command-no-jobs 3 sh -c \"printf \\\"%s\\n%s\\n\\\" Hello World\" 2>actual &&\n+\ttest_cmp expect actual\n+'\n+\n test_done\ndiff --git a/test-run-command.c b/test-run-command.c\nindex 89c7de2..f964507 100644\n--- a/test-run-command.c\n+++ b/test-run-command.c\n@@ -10,16 +10,54 @@\n \n #include \"git-compat-util.h\"\n #include \"run-command.h\"\n+#include \"argv-array.h\"\n+#include \"strbuf.h\"\n #include \n #include \n \n+static int number_callbacks;\n+static int parallel_next(struct child_process *cp,\n+\t\t\t struct strbuf *err,\n+\t\t\t void *cb,\n+\t\t\t void** task_cb)\n+{\n+\tstruct child_process *d = cb;\n+\tif (number_callbacks >= 4)\n+\t\treturn 0;\n+\n+\targv_array_pushv(&cp->args, d->argv);\n+\tstrbuf_addf(err, \"preloaded output of a child\\n\");\n+\tnumber_callbacks++;\n+\treturn 1;\n+}\n+\n+static int no_job(struct child_process *cp,\n+\t\t struct strbuf *err,\n+\t\t void *cb,\n+\t\t void** task_cb)\n+{\n+\tstrbuf_addf(err, \"no further jobs available\\n\");\n+\treturn 0;\n+}\n+\n+static int task_finished(int result,\n+\t\t\t struct child_process *cp,\n+\t\t\t struct strbuf *err,\n+\t\t\t void *pp_cb,\n+\t\t\t void *pp_task_cb)\n+{\n+\tstrbuf_addf(err, \"asking for a quick stop\\n\");\n+\treturn 1;\n+}\n+\n int main(int argc, char **argv)\n {\n \tstruct child_process proc = CHILD_PROCESS_INIT;\n+\tint jobs;\n \n \tif (argc < 3)\n \t\treturn 1;\n-\tproc.argv = (const char **)argv+2;\n+\tproc.argv = (const char **)argv + 2;\n \n \tif (!strcmp(argv[1], \"start-command-ENOENT\")) {\n \t\tif (start_command(&proc) < 0 && errno == ENOENT)\n@@ -30,6 +68,21 @@ int main(int argc, char **argv)\n \tif (!strcmp(argv[1], \"run-command\"))\n \t\texit(run_command(&proc));\n \n+\tjobs = atoi(argv[2]);\n+\tproc.argv = (const char **)argv + 3;\n+\n+\tif (!strcmp(argv[1], \"run-command-parallel\"))\n+\t\texit(run_processes_parallel(jobs, parallel_next,\n+\t\t\t\t\t NULL, NULL, &proc));\n+\n+\tif (!strcmp(argv[1], \"run-command-abort\"))\n+\t\texit(run_processes_parallel(jobs, parallel_next,\n+\t\t\t\t\t NULL, task_finished, &proc));\n+\n+\tif (!strcmp(argv[1], \"run-command-no-jobs\"))\n+\t\texit(run_processes_parallel(jobs, no_job,\n+\t\t\t\t\t NULL, task_finished, &proc));\n+\n \tfprintf(stderr, \"check usage\\n\");\n \treturn 1;\n }\n-- \n2.6.4.443.ge094245.dirty\n"},{"id":"274409","messageId":"1450121838-7069-8-git-send-email-sbeller@google.com","threadId":"40994","inReplyTo":"1450121838-7069-1-git-send-email-sbeller@google.com","subject":"[PATCH 7/8] fetch_populated_submodules: use new parallel job processing","fromName":"Stefan Beller","fromEmail":"sbeller@google.com","sentAt":"2015-12-14T19:37:17Z","receivedAt":"2015-12-14T19:37:17Z","isPatch":true,"sender":{"key":"stefanbeller@gmail.com","avatar":"https://avatars.githubusercontent.com/u/455868?v=4"},"body":"In a later patch we enable parallel processing of submodules, this\nonly adds the possibility for it. So this change should not change\nany user facing behavior.\n\nSigned-off-by: Stefan Beller \nSigned-off-by: Junio C Hamano \n---\n submodule.c | 142 +++++++++++++++++++++++++++++++++++++++++-------------------\n 1 file changed, 98 insertions(+), 44 deletions(-)\n\ndiff --git a/submodule.c b/submodule.c\nindex 8386477..6a2d786 100644\n--- a/submodule.c\n+++ b/submodule.c\n@@ -12,6 +12,7 @@\n #include \"sha1-array.h\"\n #include \"argv-array.h\"\n #include \"blob.h\"\n+#include \"thread-utils.h\"\n \n static int config_fetch_recurse_submodules = RECURSE_SUBMODULES_ON_DEMAND;\n static struct string_list changed_submodule_paths;\n@@ -610,37 +611,28 @@ static void calculate_changed_submodule_paths(void)\n \tinitialized_fetch_ref_tips = 0;\n }\n \n-int fetch_populated_submodules(const struct argv_array *options,\n-\t\t\t const char *prefix, int command_line_option,\n-\t\t\t int quiet)\n+struct submodule_parallel_fetch {\n+\tint count;\n+\tstruct argv_array args;\n+\tconst char *work_tree;\n+\tconst char *prefix;\n+\tint command_line_option;\n+\tint quiet;\n+\tint result;\n+};\n+#define SPF_INIT {0, ARGV_ARRAY_INIT, NULL, NULL, 0, 0, 0}\n+\n+static int get_next_submodule(struct child_process *cp,\n+\t\t\t struct strbuf *err, void *data, void **task_cb)\n {\n-\tint i, result = 0;\n-\tstruct child_process cp = CHILD_PROCESS_INIT;\n-\tstruct argv_array argv = ARGV_ARRAY_INIT;\n-\tconst char *work_tree = get_git_work_tree();\n-\tif (!work_tree)\n-\t\tgoto out;\n-\n-\tif (read_cache() < 0)\n-\t\tdie(\"index file corrupt\");\n-\n-\targv_array_push(&argv, \"fetch\");\n-\tfor (i = 0; i < options->argc; i++)\n-\t\targv_array_push(&argv, options->argv[i]);\n-\targv_array_push(&argv, \"--recurse-submodules-default\");\n-\t/* default value, \"--submodule-prefix\" and its value are added later */\n-\n-\tcp.env = local_repo_env;\n-\tcp.git_cmd = 1;\n-\tcp.no_stdin = 1;\n-\n-\tcalculate_changed_submodule_paths();\n+\tint ret = 0;\n+\tstruct submodule_parallel_fetch *spf = data;\n \n-\tfor (i = 0; i < active_nr; i++) {\n+\tfor ( ; spf->count < active_nr; spf->count++) {\n \t\tstruct strbuf submodule_path = STRBUF_INIT;\n \t\tstruct strbuf submodule_git_dir = STRBUF_INIT;\n \t\tstruct strbuf submodule_prefix = STRBUF_INIT;\n-\t\tconst struct cache_entry *ce = active_cache[i];\n+\t\tconst struct cache_entry *ce = active_cache[spf->count];\n \t\tconst char *git_dir, *default_argv;\n \t\tconst struct submodule *submodule;\n \n@@ -652,7 +644,7 @@ int fetch_populated_submodules(const struct argv_array *options,\n \t\t\tsubmodule = submodule_from_name(null_sha1, ce->name);\n \n \t\tdefault_argv = \"yes\";\n-\t\tif (command_line_option == RECURSE_SUBMODULES_DEFAULT) {\n+\t\tif (spf->command_line_option == RECURSE_SUBMODULES_DEFAULT) {\n \t\t\tif (submodule &&\n \t\t\t submodule->fetch_recurse !=\n \t\t\t\t\t\tRECURSE_SUBMODULES_NONE) {\n@@ -675,40 +667,102 @@ int fetch_populated_submodules(const struct argv_array *options,\n \t\t\t\t\tdefault_argv = \"on-demand\";\n \t\t\t\t}\n \t\t\t}\n-\t\t} else if (command_line_option == RECURSE_SUBMODULES_ON_DEMAND) {\n+\t\t} else if (spf->command_line_option == RECURSE_SUBMODULES_ON_DEMAND) {\n \t\t\tif (!unsorted_string_list_lookup(&changed_submodule_paths, ce->name))\n \t\t\t\tcontinue;\n \t\t\tdefault_argv = \"on-demand\";\n \t\t}\n \n-\t\tstrbuf_addf(&submodule_path, \"%s/%s\", work_tree, ce->name);\n+\t\tstrbuf_addf(&submodule_path, \"%s/%s\", spf->work_tree, ce->name);\n \t\tstrbuf_addf(&submodule_git_dir, \"%s/.git\", submodule_path.buf);\n-\t\tstrbuf_addf(&submodule_prefix, \"%s%s/\", prefix, ce->name);\n+\t\tstrbuf_addf(&submodule_prefix, \"%s%s/\", spf->prefix, ce->name);\n \t\tgit_dir = read_gitfile(submodule_git_dir.buf);\n \t\tif (!git_dir)\n \t\t\tgit_dir = submodule_git_dir.buf;\n \t\tif (is_directory(git_dir)) {\n-\t\t\tif (!quiet)\n-\t\t\t\tfprintf(stderr, \"Fetching submodule %s%s\\n\", prefix, ce->name);\n-\t\t\tcp.dir = submodule_path.buf;\n-\t\t\targv_array_push(&argv, default_argv);\n-\t\t\targv_array_push(&argv, \"--submodule-prefix\");\n-\t\t\targv_array_push(&argv, submodule_prefix.buf);\n-\t\t\tcp.argv = argv.argv;\n-\t\t\tif (run_command(&cp))\n-\t\t\t\tresult = 1;\n-\t\t\targv_array_pop(&argv);\n-\t\t\targv_array_pop(&argv);\n-\t\t\targv_array_pop(&argv);\n+\t\t\tchild_process_init(cp);\n+\t\t\tcp->dir = strbuf_detach(&submodule_path, NULL);\n+\t\t\tcp->env = local_repo_env;\n+\t\t\tcp->git_cmd = 1;\n+\t\t\tif (!spf->quiet)\n+\t\t\t\tstrbuf_addf(err, \"Fetching submodule %s%s\\n\",\n+\t\t\t\t\t spf->prefix, ce->name);\n+\t\t\targv_array_init(&cp->args);\n+\t\t\targv_array_pushv(&cp->args, spf->args.argv);\n+\t\t\targv_array_push(&cp->args, default_argv);\n+\t\t\targv_array_push(&cp->args, \"--submodule-prefix\");\n+\t\t\targv_array_push(&cp->args, submodule_prefix.buf);\n+\t\t\tret = 1;\n \t\t}\n \t\tstrbuf_release(&submodule_path);\n \t\tstrbuf_release(&submodule_git_dir);\n \t\tstrbuf_release(&submodule_prefix);\n+\t\tif (ret) {\n+\t\t\tspf->count++;\n+\t\t\treturn 1;\n+\t\t}\n \t}\n-\targv_array_clear(&argv);\n+\treturn 0;\n+}\n+\n+static int fetch_start_failure(struct child_process *cp,\n+\t\t\t struct strbuf *err,\n+\t\t\t void *cb, void *task_cb)\n+{\n+\tstruct submodule_parallel_fetch *spf = cb;\n+\n+\tspf->result = 1;\n+\n+\treturn 0;\n+}\n+\n+static int fetch_finish(int retvalue, struct child_process *cp,\n+\t\t\tstruct strbuf *err, void *cb, void *task_cb)\n+{\n+\tstruct submodule_parallel_fetch *spf = cb;\n+\n+\tif (retvalue)\n+\t\tspf->result = 1;\n+\n+\treturn 0;\n+}\n+\n+int fetch_populated_submodules(const struct argv_array *options,\n+\t\t\t const char *prefix, int command_line_option,\n+\t\t\t int quiet)\n+{\n+\tint i;\n+\tint max_parallel_jobs = 1;\n+\tstruct submodule_parallel_fetch spf = SPF_INIT;\n+\n+\tspf.work_tree = get_git_work_tree();\n+\tspf.command_line_option = command_line_option;\n+\tspf.quiet = quiet;\n+\tspf.prefix = prefix;\n+\n+\tif (!spf.work_tree)\n+\t\tgoto out;\n+\n+\tif (read_cache() < 0)\n+\t\tdie(\"index file corrupt\");\n+\n+\targv_array_push(&spf.args, \"fetch\");\n+\tfor (i = 0; i < options->argc; i++)\n+\t\targv_array_push(&spf.args, options->argv[i]);\n+\targv_array_push(&spf.args, \"--recurse-submodules-default\");\n+\t/* default value, \"--submodule-prefix\" and its value are added later */\n+\n+\tcalculate_changed_submodule_paths();\n+\trun_processes_parallel(max_parallel_jobs,\n+\t\t\t get_next_submodule,\n+\t\t\t fetch_start_failure,\n+\t\t\t fetch_finish,\n+\t\t\t &spf);\n+\n+\targv_array_clear(&spf.args);\n out:\n \tstring_list_clear(&changed_submodule_paths, 1);\n-\treturn result;\n+\treturn spf.result;\n }\n \n unsigned is_submodule_modified(const char *path, int ignore_untracked)\n-- \n2.6.4.443.ge094245.dirty\n"},{"id":"274408","messageId":"1450121838-7069-9-git-send-email-sbeller@google.com","threadId":"40994","inReplyTo":"1450121838-7069-1-git-send-email-sbeller@google.com","subject":"[PATCH 8/8] submodules: allow parallel fetching, add tests and documentation","fromName":"Stefan Beller","fromEmail":"sbeller@google.com","sentAt":"2015-12-14T19:37:18Z","receivedAt":"2015-12-14T19:37:18Z","isPatch":true,"sender":{"key":"stefanbeller@gmail.com","avatar":"https://avatars.githubusercontent.com/u/455868?v=4"},"body":"This enables the work of the previous patches.\n\nSigned-off-by: Stefan Beller \nSigned-off-by: Junio C Hamano \n---\n Documentation/fetch-options.txt | 7 +++++++\n builtin/fetch.c | 6 +++++-\n builtin/pull.c | 6 ++++++\n submodule.c | 3 +--\n submodule.h | 2 +-\n t/t5526-fetch-submodules.sh | 20 ++++++++++++++++++++\n 6 files changed, 40 insertions(+), 4 deletions(-)\n\ndiff --git a/Documentation/fetch-options.txt b/Documentation/fetch-options.txt\nindex 45583d8..6b109f6 100644\n--- a/Documentation/fetch-options.txt\n+++ b/Documentation/fetch-options.txt\n@@ -100,6 +100,13 @@ ifndef::git-pull[]\n \treference to a commit that isn't already in the local submodule\n \tclone.\n \n+-j::\n+--jobs=::\n+\tNumber of parallel children to be used for fetching submodules.\n+\tEach will fetch from different submodules, such that fetching many\n+\tsubmodules will be faster. By default submodules will be fetched\n+\tone at a time.\n+\n --no-recurse-submodules::\n \tDisable recursive fetching of submodules (this has the same effect as\n \tusing the '--recurse-submodules=no' option).\ndiff --git a/builtin/fetch.c b/builtin/fetch.c\nindex c85f347..586840d 100644\n--- a/builtin/fetch.c\n+++ b/builtin/fetch.c\n@@ -37,6 +37,7 @@ static int prune = -1; /* unspecified */\n static int all, append, dry_run, force, keep, multiple, update_head_ok, verbosity;\n static int progress = -1, recurse_submodules = RECURSE_SUBMODULES_DEFAULT;\n static int tags = TAGS_DEFAULT, unshallow, update_shallow;\n+static int max_children = 1;\n static const char *depth;\n static const char *upload_pack;\n static struct strbuf default_rla = STRBUF_INIT;\n@@ -99,6 +100,8 @@ static struct option builtin_fetch_options[] = {\n \t\t N_(\"fetch all tags and associated objects\"), TAGS_SET),\n \tOPT_SET_INT('n', NULL, &tags,\n \t\t N_(\"do not fetch all tags (--no-tags)\"), TAGS_UNSET),\n+\tOPT_INTEGER('j', \"jobs\", &max_children,\n+\t\t N_(\"number of submodules fetched in parallel\")),\n \tOPT_BOOL('p', \"prune\", &prune,\n \t\t N_(\"prune remote-tracking branches no longer on remote\")),\n \t{ OPTION_CALLBACK, 0, \"recurse-submodules\", NULL, N_(\"on-demand\"),\n@@ -1213,7 +1216,8 @@ int cmd_fetch(int argc, const char **argv, const char *prefix)\n \t\tresult = fetch_populated_submodules(&options,\n \t\t\t\t\t\t submodule_prefix,\n \t\t\t\t\t\t recurse_submodules,\n-\t\t\t\t\t\t verbosity < 0);\n+\t\t\t\t\t\t verbosity < 0,\n+\t\t\t\t\t\t max_children);\n \t\targv_array_clear(&options);\n \t}\n \ndiff --git a/builtin/pull.c b/builtin/pull.c\nindex 5145fc6..9e3c738 100644\n--- a/builtin/pull.c\n+++ b/builtin/pull.c\n@@ -95,6 +95,7 @@ static int opt_force;\n static char *opt_tags;\n static char *opt_prune;\n static char *opt_recurse_submodules;\n+static char *max_children;\n static int opt_dry_run;\n static char *opt_keep;\n static char *opt_depth;\n@@ -178,6 +179,9 @@ static struct option pull_options[] = {\n \t\tN_(\"on-demand\"),\n \t\tN_(\"control recursive fetching of submodules\"),\n \t\tPARSE_OPT_OPTARG),\n+\tOPT_PASSTHRU('j', \"jobs\", &max_children, N_(\"n\"),\n+\t\tN_(\"number of submodules pulled in parallel\"),\n+\t\tPARSE_OPT_OPTARG),\n \tOPT_BOOL(0, \"dry-run\", &opt_dry_run,\n \t\tN_(\"dry run\")),\n \tOPT_PASSTHRU('k', \"keep\", &opt_keep, NULL,\n@@ -525,6 +529,8 @@ static int run_fetch(const char *repo, const char **refspecs)\n \t\targv_array_push(&args, opt_prune);\n \tif (opt_recurse_submodules)\n \t\targv_array_push(&args, opt_recurse_submodules);\n+\tif (max_children)\n+\t\targv_array_push(&args, max_children);\n \tif (opt_dry_run)\n \t\targv_array_push(&args, \"--dry-run\");\n \tif (opt_keep)\ndiff --git a/submodule.c b/submodule.c\nindex 6a2d786..0b48734 100644\n--- a/submodule.c\n+++ b/submodule.c\n@@ -729,10 +729,9 @@ static int fetch_finish(int retvalue, struct child_process *cp,\n \n int fetch_populated_submodules(const struct argv_array *options,\n \t\t\t const char *prefix, int command_line_option,\n-\t\t\t int quiet)\n+\t\t\t int quiet, int max_parallel_jobs)\n {\n \tint i;\n-\tint max_parallel_jobs = 1;\n \tstruct submodule_parallel_fetch spf = SPF_INIT;\n \n \tspf.work_tree = get_git_work_tree();\ndiff --git a/submodule.h b/submodule.h\nindex 5507c3d..cbc0003 100644\n--- a/submodule.h\n+++ b/submodule.h\n@@ -31,7 +31,7 @@ void set_config_fetch_recurse_submodules(int value);\n void check_for_new_submodule_commits(unsigned char new_sha1[20]);\n int fetch_populated_submodules(const struct argv_array *options,\n \t\t\t const char *prefix, int command_line_option,\n-\t\t\t int quiet);\n+\t\t\t int quiet, int max_parallel_jobs);\n unsigned is_submodule_modified(const char *path, int ignore_untracked);\n int submodule_uses_gitfile(const char *path);\n int ok_to_remove_submodule(const char *path);\ndiff --git a/t/t5526-fetch-submodules.sh b/t/t5526-fetch-submodules.sh\nindex 17759b14..1241146 100755\n--- a/t/t5526-fetch-submodules.sh\n+++ b/t/t5526-fetch-submodules.sh\n@@ -71,6 +71,17 @@ test_expect_success \"fetch --recurse-submodules recurses into submodules\" '\n \ttest_i18ncmp expect.err actual.err\n '\n \n+test_expect_success \"fetch --recurse-submodules -j2 has the same output behaviour\" '\n+\tadd_upstream_commit &&\n+\t(\n+\t\tcd downstream &&\n+\t\tGIT_TRACE=$(pwd)/../trace.out git fetch --recurse-submodules -j2 2>../actual.err\n+\t) &&\n+\ttest_must_be_empty actual.out &&\n+\ttest_i18ncmp expect.err actual.err &&\n+\tgrep \"2 tasks\" trace.out\n+'\n+\n test_expect_success \"fetch alone only fetches superproject\" '\n \tadd_upstream_commit &&\n \t(\n@@ -140,6 +151,15 @@ test_expect_success \"--quiet propagates to submodules\" '\n \t! test -s actual.err\n '\n \n+test_expect_success \"--quiet propagates to parallel submodules\" '\n+\t(\n+\t\tcd downstream &&\n+\t\tgit fetch --recurse-submodules -j 2 --quiet >../actual.out 2>../actual.err\n+\t) &&\n+\t! test -s actual.out &&\n+\t! test -s actual.err\n+'\n+\n test_expect_success \"--dry-run propagates to submodules\" '\n \tadd_upstream_commit &&\n \t(\n-- \n2.6.4.443.ge094245.dirty\n"},{"id":"274418","messageId":"566F28EA.3080802@kdbg.org","threadId":"40994","inReplyTo":"1450121838-7069-7-git-send-email-sbeller@google.com","subject":"Re: [PATCH 6/8] run-command: add an asynchronous parallel child processor","fromName":"Johannes Sixt","fromEmail":"j6t@kdbg.org","sentAt":"2015-12-14T20:39:06Z","receivedAt":"2015-12-14T20:39:06Z","isPatch":true,"sender":{"key":"j6t@kdbg.org","avatar":"https://avatars.githubusercontent.com/u/14810926?v=4"},"body":"Am 14.12.2015 um 20:37 schrieb Stefan Beller:\n> This allows to run external commands in parallel with ordered output\n> on stderr.\n>\n> If we run external commands in parallel we cannot pipe the output directly\n> to the our stdout/err as it would mix up. So each process's output will\n> flow through a pipe, which we buffer. One subprocess can be directly\n> piped to out stdout/err for a low latency feedback to the user.\n>\n> Example:\n> Let's assume we have 5 submodules A,B,C,D,E and each fetch takes a\n> different amount of time as the different submodules vary in size, then\n> the output of fetches in sequential order might look like this:\n>\n> time -->\n> output: |---A---| |-B-| |-------C-------| |-D-| |-E-|\n>\n> When we schedule these submodules into maximal two parallel processes,\n> a schedule and sample output over time may look like this:\n>\n> process 1: |---A---| |-D-| |-E-|\n>\n> process 2: |-B-| |-------C-------|\n>\n> output: |---A---|B|---C-------|DE\n>\n> So A will be perceived as it would run normally in the single child\n> version. As B has finished by the time A is done, we can dump its whole\n> progress buffer on stderr, such that it looks like it finished in no\n> time. Once that is done, C is determined to be the visible child and\n> its progress will be reported in real time.\n>\n> So this way of output is really good for human consumption, as it only\n> changes the timing, not the actual output.\n>\n> For machine consumption the output needs to be prepared in the tasks,\n> by either having a prefix per line or per block to indicate whose tasks\n> output is displayed, because the output order may not follow the\n> original sequential ordering:\n>\n> |----A----| |--B--| |-C-|\n>\n> will be scheduled to be all parallel:\n>\n> process 1: |----A----|\n> process 2: |--B--|\n> process 3: |-C-|\n> output: |----A----|CB\n>\n> This happens because C finished before B did, so it will be queued for\n> output before B.\n>\n> The detection when a child has finished executing is done the same way as\n> two fold. First we check regularly if the stderr pipe still exists in an\n> interleaved manner with other actions such as checking other children\n> for their liveliness or starting new children. Once a child closed their\n> stderr stream, we assume it is stopping very soon, such that we can use\n> the `finish_command` code borrowed from the single external process\n> execution interface.\n\nI can't quite parse the first sentence in this paragraph. Perhaps \nsomething like this:\n\nTo detect when a child has finished executing, we check interleaved\nwith other actions (such as checking the liveliness of children or\nstarting new processes) whether the stderr pipe still exists. Once a\nchild closed its stderr stream, we assume it is terminating very soon,\nand use finish_command() from the single external process execution\ninterface to collect the exit status.\n\n>\n> By maintaining the strong assumption of stderr being open until the\n> very end of a child process, we can avoid other hassle such as an\n> implementation using `waitpid(-1)`, which is not implemented in Windows.\n>\n> Signed-off-by: Stefan Beller \n"},{"id":"274420","messageId":"566F2952.8000307@kdbg.org","threadId":"40994","inReplyTo":"1450121838-7069-1-git-send-email-sbeller@google.com","subject":"Re: [PATCH 0/8] Rerolling sb/submodule-parallel-fetch for the time after 2.7","fromName":"Johannes Sixt","fromEmail":"j6t@kdbg.org","sentAt":"2015-12-14T20:40:50Z","receivedAt":"2015-12-14T20:40:50Z","isPatch":true,"sender":{"key":"j6t@kdbg.org","avatar":"https://avatars.githubusercontent.com/u/14810926?v=4"},"body":"Am 14.12.2015 um 20:37 schrieb Stefan Beller:\n> I am sending out a new version for replacing sb/submodule-parallel-fetch for\n> the time after the 2.7 release.\n>\n> The content are\n> * all patches as in the branch sb/submodule-parallel-fetch\n> * inlcuding the fixups as suggested by Hannes,\n> * write a message to the debug log for better testing and debugging purposes\n> (a patch cherry picked from the series which is supposed to build on top of this)\n>\n> The patches themselves were rebased such that there are no fixup commits\n> any more, but we get things right the first time.\n>\n> The commit message of \"run-command: add an asynchronous parallel child processor\"\n> has slightly been updated to mention the fact that we don't want to use waitpid(-1)\n> but rather use the assumption of child's stderr living as long as the child itself.\n\nThanks! I rebased a version of sb/submodule-parallel-fetch that includes \nmy suggested improvements, and the result is identical to this series \nexcept for the trace output mentioned in the last bullet point.\n\nWith or without addressing my note about the commit message in 6/8:\n\nAcked-by: Johannes Sixt \n\n> Thanks,\n> Stefan\n>\n>\n> Jonathan Nieder (1):\n> submodule.c: write \"Fetching submodule \" to stderr\n>\n> Stefan Beller (7):\n> xread: poll on non blocking fds\n> xread_nonblock: add functionality to read from fds without blocking\n> strbuf: add strbuf_read_once to read without blocking\n> sigchain: add command to pop all common signals\n> run-command: add an asynchronous parallel child processor\n> fetch_populated_submodules: use new parallel job processing\n> submodules: allow parallel fetching, add tests and documentation\n>\n> Documentation/fetch-options.txt | 7 +\n> builtin/fetch.c | 6 +-\n> builtin/pull.c | 6 +\n> git-compat-util.h | 1 +\n> run-command.c | 335 ++++++++++++++++++++++++++++++++++++++++\n> run-command.h | 80 ++++++++++\n> sigchain.c | 9 ++\n> sigchain.h | 1 +\n> strbuf.c | 11 ++\n> strbuf.h | 8 +\n> submodule.c | 141 +++++++++++------\n> submodule.h | 2 +-\n> t/t0061-run-command.sh | 53 +++++++\n> t/t5526-fetch-submodules.sh | 71 ++++++---\n> test-run-command.c | 55 ++++++-\n> wrapper.c | 35 ++++-\n> 16 files changed, 747 insertions(+), 74 deletions(-)\n>\n"},{"id":"274427","messageId":"xmqqmvtciw69.fsf@gitster.mtv.corp.google.com","threadId":"40994","inReplyTo":"1450121838-7069-4-git-send-email-sbeller@google.com","subject":"Re: [PATCH 3/8] xread_nonblock: add functionality to read from fds without blocking","fromName":"Junio C Hamano","fromEmail":"gitster@pobox.com","sentAt":"2015-12-14T20:59:10Z","receivedAt":"2015-12-14T20:59:10Z","isPatch":true,"sender":{"key":"gitster@pobox.com","avatar":"https://avatars.githubusercontent.com/u/54884?v=4"},"body":"Stefan Beller writes:\n\n> Provide a wrapper to read(), similar to xread(), that restarts on\n> EINTR but not EAGAIN (or EWOULDBLOCK). This enables the caller to\n> handle polling itself, possibly polling multiple sockets or performing\n> some other action.\n\nDo you still need this (and use of this in 4/8)? The description of\na4433fd4 (run-command: remove set_nonblocking(), 2015-11-05) from\nthe previous iteration justifies the removal of set_nonblocking()\nthis way:\n\n run-command: remove set_nonblocking()\n \n strbuf_read_once can also operate on blocking file descriptors if we\n are sure they are ready. And the poll(2) we call before calling\n this ensures that this is the case.\n\nUpdated run-command in this reroll lacks set_nonblocking(), and does\nhave the poll(2) before it calls strbuf_read_once(). Which means\nthat xread_nonblock() introduced here and used by [4/8] would read a\nfile descriptor that is not marked as nonblock, the read(2) in there\nwould never error-return with EWOULDBLOCK, and would be identical to \nxread() updated by [2/8] in this reroll.\n\nSo it appears to me that you can lose this and call xread() in [4/8]?\n\nAhh, there is a difference if the file descriptor the caller feeds\nstrbuf_read_once() happens to be marked as nonblock. read_once()\nwants to return without doing the poll() in such a case. Even\nthough this series would not introduce any use of a nonblocking file\ndescriptor, as a general API function, [4/8] must be prepared for\nsuch a future caller, hence [3/8] is needed.\n\nOK, thanks.\n"},{"id":"274428","messageId":"xmqqio40iw3p.fsf@gitster.mtv.corp.google.com","threadId":"40994","inReplyTo":"566F2952.8000307@kdbg.org","subject":"Re: [PATCH 0/8] Rerolling sb/submodule-parallel-fetch for the time after 2.7","fromName":"Junio C Hamano","fromEmail":"gitster@pobox.com","sentAt":"2015-12-14T21:00:42Z","receivedAt":"2015-12-14T21:00:42Z","isPatch":true,"sender":{"key":"gitster@pobox.com","avatar":"https://avatars.githubusercontent.com/u/54884?v=4"},"body":"Johannes Sixt writes:\n\n> Am 14.12.2015 um 20:37 schrieb Stefan Beller:\n>> I am sending out a new version for replacing sb/submodule-parallel-fetch for\n>> the time after the 2.7 release.\n>>\n>> The content are\n>> * all patches as in the branch sb/submodule-parallel-fetch\n>> * inlcuding the fixups as suggested by Hannes,\n>> * write a message to the debug log for better testing and debugging purposes\n>> (a patch cherry picked from the series which is supposed to build on top of this)\n>>\n>> The patches themselves were rebased such that there are no fixup commits\n>> any more, but we get things right the first time.\n>>\n>> The commit message of \"run-command: add an asynchronous parallel child processor\"\n>> has slightly been updated to mention the fact that we don't want to use waitpid(-1)\n>> but rather use the assumption of child's stderr living as long as the child itself.\n>\n> Thanks! I rebased a version of sb/submodule-parallel-fetch that\n> includes my suggested improvements, and the result is identical to\n> this series except for the trace output mentioned in the last bullet\n> point.\n>\n> With or without addressing my note about the commit message in 6/8:\n>\n> Acked-by: Johannes Sixt \n\nThanks, both. This round does look very clean to build on top.\n"},{"id":"274439","messageId":"CAGZ79kbseHv+gbjxFHH8nO_QV-8SS+7u=LYVQ0_K5u39rD0uGQ@mail.gmail.com","threadId":"40994","inReplyTo":"566F28EA.3080802@kdbg.org","subject":"Re: [PATCH 6/8] run-command: add an asynchronous parallel child processor","fromName":"Stefan Beller","fromEmail":"sbeller@google.com","sentAt":"2015-12-14T21:40:28Z","receivedAt":"2015-12-14T21:40:28Z","isPatch":true,"sender":{"key":"stefanbeller@gmail.com","avatar":"https://avatars.githubusercontent.com/u/455868?v=4"},"body":"On Mon, Dec 14, 2015 at 12:39 PM, Johannes Sixt wrote:\n>\n> I can't quite parse the first sentence in this paragraph. Perhaps something\n> like this:\n>\n> To detect when a child has finished executing, we check interleaved\n> with other actions (such as checking the liveliness of children or\n> starting new processes) whether the stderr pipe still exists. Once a\n> child closed its stderr stream, we assume it is terminating very soon,\n> and use finish_command() from the single external process execution\n> interface to collect the exit status.\n\nSounds much better than my words. If a resend is necessary, I'll have your\nreworded version of the paragraph instead.\n\n>\n>\n>>\n>> By maintaining the strong assumption of stderr being open until the\n>> very end of a child process, we can avoid other hassle such as an\n>> implementation using `waitpid(-1)`, which is not implemented in Windows.\n>>\n>> Signed-off-by: Stefan Beller \n>\n>\n"},{"id":"274458","messageId":"CAPig+cQoranAhJKSZm6jP-hYutkoXkf6461sY1v5NseQVTNL_g@mail.gmail.com","threadId":"40994","inReplyTo":"1450121838-7069-3-git-send-email-sbeller@google.com","subject":"Re: [PATCH 2/8] xread: poll on non blocking fds","fromName":"Eric Sunshine","fromEmail":"ericsunshine@gmail.com","sentAt":"2015-12-14T22:58:28Z","receivedAt":"2015-12-14T22:58:28Z","isPatch":true,"sender":{"key":"ericsunshine@gmail.com","avatar":null},"body":"On Mon, Dec 14, 2015 at 2:37 PM, Stefan Beller wrote:\n> From the man page:\n> EAGAIN The file descriptor fd refers to a file other than a socket\n> and has been marked nonblocking (O_NONBLOCK), and the read\n> would block.\n>\n> EAGAIN or EWOULDBLOCK\n> The file descriptor fd refers to a socket and has been marked\n> nonblocking (O_NONBLOCK), and the read would block. POSIX.1-2001\n> allows either error to be returned for this case, and does not\n> require these constants to have the same value, so a portable\n> application should check for both possibilities.\n>\n> If we get an EAGAIN or EWOULDBLOCK the fd must have set O_NONBLOCK.\n> As the intent of xread is to read as much as possible either until the\n> fd is EOF or an actual error occurs, we can ease the feeder of the fd\n> by not spinning the whole time, but rather wait for it politely by not\n> busy waiting.\n>\n> We should not care if the call to poll failed, as we're in an infinite\n> loop and can only get out with the correct read().\n>\n> Signed-off-by: Stefan Beller \n> Signed-off-by: Junio C Hamano \n> ---\n> diff --git a/wrapper.c b/wrapper.c\n> index 6fcaa4d..4f720fe 100644\n> --- a/wrapper.c\n> +++ b/wrapper.c\n> @@ -236,8 +236,17 @@ ssize_t xread(int fd, void *buf, size_t len)\n> len = MAX_IO_SIZE;\n> while (1) {\n> nr = read(fd, buf, len);\n> - if ((nr < 0) && (errno == EAGAIN || errno == EINTR))\n> - continue;\n> + if (nr < 0) {\n> + if (errno == EINTR)\n> + continue;\n> + if (errno == EAGAIN || errno == EWOULDBLOCK) {\n> + struct pollfd pfd;\n> + pfd.events = POLLIN;\n> + pfd.fd = fd;\n> + /* We deliberately ignore the return value */\n\nThis comment tells us what the code itself already says, but not why\nthe value is being ignored. The reader still has to consult the commit\nmessage to learn that detail, which makes the value of the comment\nquestionable.\n\n> + poll(&pfd, 1, -1);\n> + }\n> + }\n> return nr;\n> }\n> }\n> --\n> 2.6.4.443.ge094245.dirty\n>\n"},{"id":"274459","messageId":"CAPig+cSiE8rJD8ohgW99SBJMFE8cJ6UrHKeAucj4fTEmUW7Ntg@mail.gmail.com","threadId":"40994","inReplyTo":"1450121838-7069-4-git-send-email-sbeller@google.com","subject":"Re: [PATCH 3/8] xread_nonblock: add functionality to read from fds without blocking","fromName":"Eric Sunshine","fromEmail":"ericsunshine@gmail.com","sentAt":"2015-12-14T23:03:15Z","receivedAt":"2015-12-14T23:03:15Z","isPatch":true,"sender":{"key":"ericsunshine@gmail.com","avatar":null},"body":"On Mon, Dec 14, 2015 at 2:37 PM, Stefan Beller wrote:\n> Provide a wrapper to read(), similar to xread(), that restarts on\n> EINTR but not EAGAIN (or EWOULDBLOCK). This enables the caller to\n> handle polling itself, possibly polling multiple sockets or performing\n> some other action.\n>\n> Signed-off-by: Stefan Beller \n> ---\n> diff --git a/wrapper.c b/wrapper.c\n> @@ -252,6 +252,28 @@ ssize_t xread(int fd, void *buf, size_t len)\n> + * xread_nonblock() is the same a read(), but it automatically restarts read()\n> + * interrupted operations (EINTR). xread_nonblock() DOES NOT GUARANTEE that\n> + * \"len\" bytes is read. EWOULDBLOCK is turned into EAGAIN.\n\nThe last sentence is confusing. From the commit message, we learn that\nthis function doesn't care about EAGAIN or EWOULDBLOCK, yet the above\ncomment seems to imply that it does. What it really ought to be saying\nis that \"as a convenience, errno is transformed from EWOULDBLOCK to\nEAGAIN so that the caller only has to check for EAGAIN\".\n\n(It also feels weird that this should be messing with errno at all,\nbut that's a different issue...)\n\n> + */\n> +ssize_t xread_nonblock(int fd, void *buf, size_t len)\n> +{\n> + ssize_t nr;\n> + if (len > MAX_IO_SIZE)\n> + len = MAX_IO_SIZE;\n> + while (1) {\n> + nr = read(fd, buf, len);\n> + if (nr < 0) {\n> + if (errno == EINTR)\n> + continue;\n> + if (errno == EWOULDBLOCK)\n> + errno = EAGAIN;\n> + }\n> + return nr;\n> + }\n> +}\n"},{"id":"274460","messageId":"CAPig+cTbQXJPu5WHqCXDJL-s0XzB+PdOX9akoXHH1DmsLU5phQ@mail.gmail.com","threadId":"40994","inReplyTo":"CAPig+cSiE8rJD8ohgW99SBJMFE8cJ6UrHKeAucj4fTEmUW7Ntg@mail.gmail.com","subject":"Re: [PATCH 3/8] xread_nonblock: add functionality to read from fds without blocking","fromName":"Eric Sunshine","fromEmail":"ericsunshine@gmail.com","sentAt":"2015-12-14T23:05:10Z","receivedAt":"2015-12-14T23:05:10Z","isPatch":true,"sender":{"key":"ericsunshine@gmail.com","avatar":null},"body":"On Mon, Dec 14, 2015 at 6:03 PM, Eric Sunshine wrote:\n> On Mon, Dec 14, 2015 at 2:37 PM, Stefan Beller wrote:\n>> Provide a wrapper to read(), similar to xread(), that restarts on\n>> EINTR but not EAGAIN (or EWOULDBLOCK). This enables the caller to\n>> handle polling itself, possibly polling multiple sockets or performing\n>> some other action.\n>>\n>> Signed-off-by: Stefan Beller \n>> ---\n>> diff --git a/wrapper.c b/wrapper.c\n>> @@ -252,6 +252,28 @@ ssize_t xread(int fd, void *buf, size_t len)\n>> + * xread_nonblock() is the same a read(), but it automatically restarts read()\n>> + * interrupted operations (EINTR). xread_nonblock() DOES NOT GUARANTEE that\n>> + * \"len\" bytes is read. EWOULDBLOCK is turned into EAGAIN.\n>\n> The last sentence is confusing. From the commit message, we learn that\n> this function doesn't care about EAGAIN or EWOULDBLOCK, yet the above\n> comment seems to imply that it does. What it really ought to be saying\n> is that \"as a convenience, errno is transformed from EWOULDBLOCK to\n> EAGAIN so that the caller only has to check for EAGAIN\".\n\nI forgot to mention that the mutation of EWOULDBLOCK into EAGAIN is\nsomething that should be described in the header rather than here at\nthe source. In fact, the entire comment block above this function is\nmore suitable in the header file.\n"},{"id":"274461","messageId":"CAGZ79ka6RB_RFxfTaXmV+9fyCmnnKcKZdRVB1fMywO97F1sbSw@mail.gmail.com","threadId":"40994","inReplyTo":"CAPig+cQoranAhJKSZm6jP-hYutkoXkf6461sY1v5NseQVTNL_g@mail.gmail.com","subject":"Re: [PATCH 2/8] xread: poll on non blocking fds","fromName":"Stefan Beller","fromEmail":"sbeller@google.com","sentAt":"2015-12-14T23:07:11Z","receivedAt":"2015-12-14T23:07:11Z","isPatch":true,"sender":{"key":"stefanbeller@gmail.com","avatar":"https://avatars.githubusercontent.com/u/455868?v=4"},"body":"On Mon, Dec 14, 2015 at 2:58 PM, Eric Sunshine wrote:\n>> + /* We deliberately ignore the return value */\n>\n> This comment tells us what the code itself already says, but not why\n> the value is being ignored. The reader still has to consult the commit\n> message to learn that detail, which makes the value of the comment\n> questionable.\n\nIt at least tells you it's not because of sloppiness. ;)\nI'll elaborate that comment a bit further in a resend though.\n\nThanks,\nStefan\n"},{"id":"274463","messageId":"xmqqmvtchbh7.fsf@gitster.mtv.corp.google.com","threadId":"40994","inReplyTo":"CAPig+cQoranAhJKSZm6jP-hYutkoXkf6461sY1v5NseQVTNL_g@mail.gmail.com","subject":"Re: [PATCH 2/8] xread: poll on non blocking fds","fromName":"Junio C Hamano","fromEmail":"gitster@pobox.com","sentAt":"2015-12-14T23:11:32Z","receivedAt":"2015-12-14T23:11:32Z","isPatch":true,"sender":{"key":"gitster@pobox.com","avatar":"https://avatars.githubusercontent.com/u/54884?v=4"},"body":"Eric Sunshine writes:\n\n> This comment tells us what the code itself already says, but not why\n> the value is being ignored. The reader still has to consult the commit\n> message to learn that detail, which makes the value of the comment\n> questionable.\n\nLet's do this for now, then.\n\n-- >8 --\nFrom: Stefan Beller \nDate: Mon, 14 Dec 2015 11:37:12 -0800\nSubject: [PATCH] xread: poll on non blocking fds\n\nThe man page of read(2) says:\n\n EAGAIN The file descriptor fd refers to a file other than a socket\n\t and has been marked nonblocking (O_NONBLOCK), and the read\n\t would block.\n\n EAGAIN or EWOULDBLOCK\n\t The file descriptor fd refers to a socket and has been marked\n\t nonblocking (O_NONBLOCK), and the read would block. POSIX.1-2001\n\t allows either error to be returned for this case, and does not\n\t require these constants to have the same value, so a portable\n\t application should check for both possibilities.\n\nIf we get an EAGAIN or EWOULDBLOCK the fd must have set O_NONBLOCK.\nAs the intent of xread is to read as much as possible either until the\nfd is EOF or an actual error occurs, we can ease the feeder of the fd\nby not spinning the whole time, but rather wait for it politely by not\nbusy waiting.\n\nWe should not care if the call to poll failed, as we're in an infinite\nloop and can only get out with the correct read().\n\nSigned-off-by: Stefan Beller \nAcked-by: Johannes Sixt \nSigned-off-by: Junio C Hamano \n---\n wrapper.c | 20 ++++++++++++++++++--\n 1 file changed, 18 insertions(+), 2 deletions(-)\n\ndiff --git a/wrapper.c b/wrapper.c\nindex 6fcaa4d..1770efa 100644\n--- a/wrapper.c\n+++ b/wrapper.c\n@@ -236,8 +236,24 @@ ssize_t xread(int fd, void *buf, size_t len)\n \t len = MAX_IO_SIZE;\n \twhile (1) {\n \t\tnr = read(fd, buf, len);\n-\t\tif ((nr < 0) && (errno == EAGAIN || errno == EINTR))\n-\t\t\tcontinue;\n+\t\tif (nr < 0) {\n+\t\t\tif (errno == EINTR)\n+\t\t\t\tcontinue;\n+\t\t\tif (errno == EAGAIN || errno == EWOULDBLOCK) {\n+\t\t\t\tstruct pollfd pfd;\n+\t\t\t\tpfd.events = POLLIN;\n+\t\t\t\tpfd.fd = fd;\n+\t\t\t\t/*\n+\t\t\t\t * it is OK if this poll() failed; we\n+\t\t\t\t * want to leave this infinite loop\n+\t\t\t\t * only when read() returns with\n+\t\t\t\t * success, or an expected failure,\n+\t\t\t\t * which would be checked by the next\n+\t\t\t\t * call to read(2).\n+\t\t\t\t */\n+\t\t\t\tpoll(&pfd, 1, -1);\n+\t\t\t}\n+\t\t}\n \t\treturn nr;\n \t}\n }\n-- \n2.7.0-rc0-109-gb762328\n"},{"id":"274464","messageId":"CAGZ79kZxp-FVty9uydy0-k6JiFJduLD3-UuxLdJsL0aRWKgs3Q@mail.gmail.com","threadId":"40994","inReplyTo":"xmqqmvtchbh7.fsf@gitster.mtv.corp.google.com","subject":"Re: [PATCH 2/8] xread: poll on non blocking fds","fromName":"Stefan Beller","fromEmail":"sbeller@google.com","sentAt":"2015-12-14T23:14:08Z","receivedAt":"2015-12-14T23:14:08Z","isPatch":true,"sender":{"key":"stefanbeller@gmail.com","avatar":"https://avatars.githubusercontent.com/u/455868?v=4"},"body":"On Mon, Dec 14, 2015 at 3:11 PM, Junio C Hamano wrote:\n> Eric Sunshine writes:\n>\n>> This comment tells us what the code itself already says, but not why\n>> the value is being ignored. The reader still has to consult the commit\n>> message to learn that detail, which makes the value of the comment\n>> questionable.\n>\n> Let's do this for now, then.\n\nThat looks good to me. I'll pick it up for the resend.\n\n>\n> -- >8 --\n> From: Stefan Beller \n> Date: Mon, 14 Dec 2015 11:37:12 -0800\n> Subject: [PATCH] xread: poll on non blocking fds\n>\n> The man page of read(2) says:\n>\n> EAGAIN The file descriptor fd refers to a file other than a socket\n> and has been marked nonblocking (O_NONBLOCK), and the read\n> would block.\n>\n> EAGAIN or EWOULDBLOCK\n> The file descriptor fd refers to a socket and has been marked\n> nonblocking (O_NONBLOCK), and the read would block. POSIX.1-2001\n> allows either error to be returned for this case, and does not\n> require these constants to have the same value, so a portable\n> application should check for both possibilities.\n>\n> If we get an EAGAIN or EWOULDBLOCK the fd must have set O_NONBLOCK.\n> As the intent of xread is to read as much as possible either until the\n> fd is EOF or an actual error occurs, we can ease the feeder of the fd\n> by not spinning the whole time, but rather wait for it politely by not\n> busy waiting.\n>\n> We should not care if the call to poll failed, as we're in an infinite\n> loop and can only get out with the correct read().\n>\n> Signed-off-by: Stefan Beller \n> Acked-by: Johannes Sixt \n> Signed-off-by: Junio C Hamano \n> ---\n> wrapper.c | 20 ++++++++++++++++++--\n> 1 file changed, 18 insertions(+), 2 deletions(-)\n>\n> diff --git a/wrapper.c b/wrapper.c\n> index 6fcaa4d..1770efa 100644\n> --- a/wrapper.c\n> +++ b/wrapper.c\n> @@ -236,8 +236,24 @@ ssize_t xread(int fd, void *buf, size_t len)\n> len = MAX_IO_SIZE;\n> while (1) {\n> nr = read(fd, buf, len);\n> - if ((nr < 0) && (errno == EAGAIN || errno == EINTR))\n> - continue;\n> + if (nr < 0) {\n> + if (errno == EINTR)\n> + continue;\n> + if (errno == EAGAIN || errno == EWOULDBLOCK) {\n> + struct pollfd pfd;\n> + pfd.events = POLLIN;\n> + pfd.fd = fd;\n> + /*\n> + * it is OK if this poll() failed; we\n> + * want to leave this infinite loop\n> + * only when read() returns with\n> + * success, or an expected failure,\n> + * which would be checked by the next\n> + * call to read(2).\n> + */\n> + poll(&pfd, 1, -1);\n> + }\n> + }\n> return nr;\n> }\n> }\n> --\n> 2.7.0-rc0-109-gb762328\n>\n"},{"id":"274465","messageId":"xmqqio40hbam.fsf@gitster.mtv.corp.google.com","threadId":"40994","inReplyTo":"CAPig+cSiE8rJD8ohgW99SBJMFE8cJ6UrHKeAucj4fTEmUW7Ntg@mail.gmail.com","subject":"Re: [PATCH 3/8] xread_nonblock: add functionality to read from fds without blocking","fromName":"Junio C Hamano","fromEmail":"gitster@pobox.com","sentAt":"2015-12-14T23:15:29Z","receivedAt":"2015-12-14T23:15:29Z","isPatch":true,"sender":{"key":"gitster@pobox.com","avatar":"https://avatars.githubusercontent.com/u/54884?v=4"},"body":"Eric Sunshine writes:\n\n> The last sentence is confusing. From the commit message, we learn that\n> this function doesn't care about EAGAIN or EWOULDBLOCK, yet the above\n> comment seems to imply that it does. What it really ought to be saying\n> is that \"as a convenience, errno is transformed from EWOULDBLOCK to\n> EAGAIN so that the caller only has to check for EAGAIN\".\n\nLet's do this for now, then.\n\n-- >8 --\nFrom: Stefan Beller \nDate: Mon, 14 Dec 2015 11:37:13 -0800\nSubject: [PATCH] xread_nonblock: add functionality to read from fds without blocking\n\nProvide a wrapper to read(), similar to xread(), that restarts on\nEINTR but not EAGAIN (or EWOULDBLOCK). This enables the caller to\nhandle polling itself, possibly polling multiple sockets or performing\nsome other action.\n\nHelped-by: Jacob Keller \nHelped-by: Jeff King ,\nHelped-by: Junio C Hamano \nSigned-off-by: Stefan Beller \nAcked-by: Johannes Sixt \nSigned-off-by: Junio C Hamano \n---\n git-compat-util.h | 1 +\n wrapper.c | 24 ++++++++++++++++++++++++\n 2 files changed, 25 insertions(+)\n\ndiff --git a/git-compat-util.h b/git-compat-util.h\nindex 8e39867..87456a3 100644\n--- a/git-compat-util.h\n+++ b/git-compat-util.h\n@@ -723,6 +723,7 @@ extern void *xmmap(void *start, size_t length, int prot, int flags, int fd, off_\n extern void *xmmap_gently(void *start, size_t length, int prot, int flags, int fd, off_t offset);\n extern int xopen(const char *path, int flags, ...);\n extern ssize_t xread(int fd, void *buf, size_t len);\n+extern ssize_t xread_nonblock(int fd, void *buf, size_t len);\n extern ssize_t xwrite(int fd, const void *buf, size_t len);\n extern ssize_t xpread(int fd, void *buf, size_t len, off_t offset);\n extern int xdup(int fd);\ndiff --git a/wrapper.c b/wrapper.c\nindex 1770efa..0b5b03d 100644\n--- a/wrapper.c\n+++ b/wrapper.c\n@@ -259,6 +259,30 @@ ssize_t xread(int fd, void *buf, size_t len)\n }\n \n /*\n+ * xread_nonblock() automatically restarts interrupted operations\n+ * (EINTR). xread_nonblock() DOES NOT GUARANTEE that \"len\" bytes is\n+ * read. For convenience to callers that mark the file descriptor\n+ * non-blocking, EWOULDBLOCK is turned into EAGAIN to allow them to\n+ * check only for EAGAIN (POSIX.1 allows either to be returned).\n+ */\n+ssize_t xread_nonblock(int fd, void *buf, size_t len)\n+{\n+\tssize_t nr;\n+\tif (len > MAX_IO_SIZE)\n+\t\tlen = MAX_IO_SIZE;\n+\twhile (1) {\n+\t\tnr = read(fd, buf, len);\n+\t\tif (nr < 0) {\n+\t\t\tif (errno == EINTR)\n+\t\t\t\tcontinue;\n+\t\t\tif (errno == EWOULDBLOCK)\n+\t\t\t\terrno = EAGAIN;\n+\t\t}\n+\t\treturn nr;\n+\t}\n+}\n+\n+/*\n * xwrite() is the same a write(), but it automatically restarts write()\n * operations with a recoverable error (EAGAIN and EINTR). xwrite() DOES NOT\n * GUARANTEE that \"len\" bytes is written even if the operation is successful.\n-- \n2.7.0-rc0-109-gb762328\n"},{"id":"274466","messageId":"CAPig+cQUGCFZnOxjuFaYNNhLqfdS7thrUQKqNkr5=0Hr4OkyMw@mail.gmail.com","threadId":"40994","inReplyTo":"1450121838-7069-5-git-send-email-sbeller@google.com","subject":"Re: [PATCH 4/8] strbuf: add strbuf_read_once to read without blocking","fromName":"Eric Sunshine","fromEmail":"ericsunshine@gmail.com","sentAt":"2015-12-14T23:16:39Z","receivedAt":"2015-12-14T23:16:39Z","isPatch":true,"sender":{"key":"ericsunshine@gmail.com","avatar":null},"body":"On Mon, Dec 14, 2015 at 2:37 PM, Stefan Beller wrote:\n> The new call will read from a file descriptor into a strbuf once. The\n> underlying call xread_nonblock is meant to execute without blocking if\n> the file descriptor is set to O_NONBLOCK. It is a bug to call\n> strbuf_read_once on a file descriptor which would block.\n>\n> Signed-off-by: Stefan Beller \n> Signed-off-by: Junio C Hamano \n> ---\n> diff --git a/strbuf.h b/strbuf.h\n> @@ -367,6 +367,14 @@ extern size_t strbuf_fread(struct strbuf *, size_t, FILE *);\n> extern ssize_t strbuf_read(struct strbuf *, int fd, size_t hint);\n>\n> /**\n> + * Returns the number of new bytes appended to the sb.\n> + * Negative return value signals there was an error returned from\n> + * underlying read(2), in which case the caller should check errno.\n> + * e.g. errno == EAGAIN when the read may have blocked.\n> + */\n> +extern ssize_t strbuf_read_once(struct strbuf *, int fd, size_t hint);\n\nstrbuf_read_once() is a rather opaque name; without reading the\ndocumentation, it's difficult to figure out what it means. I wonder if\nstrbuf_read_nonblock() or something would be clearer?\n"},{"id":"274467","messageId":"CAGZ79kZK6+f972kF5jx11hjviW3cKtR7xsdw3dYXS48XnC1UqQ@mail.gmail.com","threadId":"40994","inReplyTo":"CAPig+cQUGCFZnOxjuFaYNNhLqfdS7thrUQKqNkr5=0Hr4OkyMw@mail.gmail.com","subject":"Re: [PATCH 4/8] strbuf: add strbuf_read_once to read without blocking","fromName":"Stefan Beller","fromEmail":"sbeller@google.com","sentAt":"2015-12-14T23:27:50Z","receivedAt":"2015-12-14T23:27:50Z","isPatch":true,"sender":{"key":"stefanbeller@gmail.com","avatar":"https://avatars.githubusercontent.com/u/455868?v=4"},"body":"On Mon, Dec 14, 2015 at 3:16 PM, Eric Sunshine wrote:\n> On Mon, Dec 14, 2015 at 2:37 PM, Stefan Beller wrote:\n>> The new call will read from a file descriptor into a strbuf once. The\n>> underlying call xread_nonblock is meant to execute without blocking if\n>> the file descriptor is set to O_NONBLOCK. It is a bug to call\n>> strbuf_read_once on a file descriptor which would block.\n>>\n>> Signed-off-by: Stefan Beller \n>> Signed-off-by: Junio C Hamano \n>> ---\n>> diff --git a/strbuf.h b/strbuf.h\n>> @@ -367,6 +367,14 @@ extern size_t strbuf_fread(struct strbuf *, size_t, FILE *);\n>> extern ssize_t strbuf_read(struct strbuf *, int fd, size_t hint);\n>>\n>> /**\n>> + * Returns the number of new bytes appended to the sb.\n>> + * Negative return value signals there was an error returned from\n>> + * underlying read(2), in which case the caller should check errno.\n>> + * e.g. errno == EAGAIN when the read may have blocked.\n>> + */\n>> +extern ssize_t strbuf_read_once(struct strbuf *, int fd, size_t hint);\n>\n> strbuf_read_once() is a rather opaque name; without reading the\n> documentation, it's difficult to figure out what it means. I wonder if\n> strbuf_read_nonblock() or something would be clearer?\n\nWell the underlying read call can block if the fd is not marked for nonblocking,\nso I would not name it _nonblock.\nI just realize this same argument would make the naming moot for the previous\npatch though. (xread_nonblock may block if not marked unblocking)\n\nCurrently we really want is a read once and do not try to grab as much\nas possible,\nbut just return quickly. We do not do the non blocking setup, as we deemed that\nunneeded because of the preceding poll in a higher layer to signal we have data\nthere to read.\n\nJunio suggested in the discussion [4/8] maybe we can just use xread\nand strbuf_read\nin this series, so I am tempted to drop patches {3,4}/8 as that makes\nsense to me.\nFor non blocking stuff we can later re introduce those helper functions though.\n"},{"id":"274468","messageId":"20151214235736.GA26133@sigill.intra.peff.net","threadId":"40994","inReplyTo":"xmqqio40hbam.fsf@gitster.mtv.corp.google.com","subject":"Re: [PATCH 3/8] xread_nonblock: add functionality to read from fds without blocking","fromName":"Jeff King","fromEmail":"peff@peff.net","sentAt":"2015-12-14T23:57:37Z","receivedAt":"2015-12-14T23:57:37Z","isPatch":true,"sender":{"key":"peff@peff.net","avatar":"https://avatars.githubusercontent.com/u/45925?v=4"},"body":"On Mon, Dec 14, 2015 at 03:15:29PM -0800, Junio C Hamano wrote:\n\n> -- >8 --\n> From: Stefan Beller \n> Date: Mon, 14 Dec 2015 11:37:13 -0800\n> Subject: [PATCH] xread_nonblock: add functionality to read from fds without blocking\n> \n> Provide a wrapper to read(), similar to xread(), that restarts on\n> EINTR but not EAGAIN (or EWOULDBLOCK). This enables the caller to\n> handle polling itself, possibly polling multiple sockets or performing\n> some other action.\n\nThis makes me wonder why we restart xread() on EAGAIN in the first\nplace.\n\nOn EINTR, sure; signals can come and we want to keep going. But if do\nnot have non-blocking descriptors, it should never happen, right?\n\nAre we trying to protect ourselves against somebody _else_ giving us a\nnon-blocking descriptor? In that case we'll quietly spin and waste CPU.\nWhich isn't great, but perhaps better than returning an error.\n\n-Peff\n"},{"id":"274470","messageId":"CAGZ79kZGjCy-o=2hO22=4=n2JqUsEG+dqOZFP4Hhf5E72B-_JA@mail.gmail.com","threadId":"40994","inReplyTo":"20151214235736.GA26133@sigill.intra.peff.net","subject":"Re: [PATCH 3/8] xread_nonblock: add functionality to read from fds without blocking","fromName":"Stefan Beller","fromEmail":"sbeller@google.com","sentAt":"2015-12-15T00:09:01Z","receivedAt":"2015-12-15T00:09:01Z","isPatch":true,"sender":{"key":"stefanbeller@gmail.com","avatar":"https://avatars.githubusercontent.com/u/455868?v=4"},"body":"On Mon, Dec 14, 2015 at 3:57 PM, Jeff King wrote:\n> On Mon, Dec 14, 2015 at 03:15:29PM -0800, Junio C Hamano wrote:\n>\n>> -- >8 --\n>> From: Stefan Beller \n>> Date: Mon, 14 Dec 2015 11:37:13 -0800\n>> Subject: [PATCH] xread_nonblock: add functionality to read from fds without blocking\n>>\n>> Provide a wrapper to read(), similar to xread(), that restarts on\n>> EINTR but not EAGAIN (or EWOULDBLOCK). This enables the caller to\n>> handle polling itself, possibly polling multiple sockets or performing\n>> some other action.\n>\n> This makes me wonder why we restart xread() on EAGAIN in the first\n> place.\n>\n> On EINTR, sure; signals can come and we want to keep going. But if do\n> not have non-blocking descriptors, it should never happen, right?\n\nright.\n\n>\n> Are we trying to protect ourselves against somebody _else_ giving us a\n> non-blocking descriptor? In that case we'll quietly spin and waste CPU.\n> Which isn't great, but perhaps better than returning an error.\n\nYes.\nThis sounds like a good reasoning for 2/8 (add in the poll, so we are\nmore polite), though.\n\nThis patch is a prerequisite for 4/8, which explicitly doesn't want to loop\nbut a quick return. Maybe we could even drop this patch and just use\n`read` as is in 4/8. Looking from a higher level perspective, we don't care\nabout strbuf_read_nonblocking to return after a signal without retry.\n\n>\n> -Peff\n"},{"id":"274471","messageId":"20151215001642.GA26409@sigill.intra.peff.net","threadId":"40994","inReplyTo":"CAGZ79kZGjCy-o=2hO22=4=n2JqUsEG+dqOZFP4Hhf5E72B-_JA@mail.gmail.com","subject":"Re: [PATCH 3/8] xread_nonblock: add functionality to read from fds without blocking","fromName":"Jeff King","fromEmail":"peff@peff.net","sentAt":"2015-12-15T00:16:42Z","receivedAt":"2015-12-15T00:16:42Z","isPatch":true,"sender":{"key":"peff@peff.net","avatar":"https://avatars.githubusercontent.com/u/45925?v=4"},"body":"On Mon, Dec 14, 2015 at 04:09:01PM -0800, Stefan Beller wrote:\n\n> > Are we trying to protect ourselves against somebody _else_ giving us a\n> > non-blocking descriptor? In that case we'll quietly spin and waste CPU.\n> > Which isn't great, but perhaps better than returning an error.\n> \n> Yes.\n> This sounds like a good reasoning for 2/8 (add in the poll, so we are\n> more polite), though.\n> \n> This patch is a prerequisite for 4/8, which explicitly doesn't want to loop\n> but a quick return. Maybe we could even drop this patch and just use\n> `read` as is in 4/8. Looking from a higher level perspective, we don't care\n> about strbuf_read_nonblocking to return after a signal without retry.\n\nI was actually thinking about simply teaching xread() not to worry about\nEAGAIN, but that would probably be a regression in the \"whoops, somebody\ngave us a non-blocking stdin!\" case.\n\nBut yeah, I think simply using xread() as-is in strbuf_read_once (or\nwhatever it ends up being called) is OK. I think all of the\n_intentionally_ non-blocking descriptors are gone in this iteration,\nright? So the caller of strbuf_read_once expects to have to call poll()\nor to block. And that's what xread() does.\n\n-Peff\n"},{"id":"274472","messageId":"CAGZ79kbLHNtxcwhZz=tHpJB2XnxMeuEJBG=PmoAbcVF4Wzno2g@mail.gmail.com","threadId":"40994","inReplyTo":"20151215001642.GA26409@sigill.intra.peff.net","subject":"Re: [PATCH 3/8] xread_nonblock: add functionality to read from fds without blocking","fromName":"Stefan Beller","fromEmail":"sbeller@google.com","sentAt":"2015-12-15T00:25:18Z","receivedAt":"2015-12-15T00:25:18Z","isPatch":true,"sender":{"key":"stefanbeller@gmail.com","avatar":"https://avatars.githubusercontent.com/u/455868?v=4"},"body":"On Mon, Dec 14, 2015 at 4:16 PM, Jeff King wrote:\n> On Mon, Dec 14, 2015 at 04:09:01PM -0800, Stefan Beller wrote:\n>\n>> > Are we trying to protect ourselves against somebody _else_ giving us a\n>> > non-blocking descriptor? In that case we'll quietly spin and waste CPU.\n>> > Which isn't great, but perhaps better than returning an error.\n>>\n>> Yes.\n>> This sounds like a good reasoning for 2/8 (add in the poll, so we are\n>> more polite), though.\n>>\n>> This patch is a prerequisite for 4/8, which explicitly doesn't want to loop\n>> but a quick return. Maybe we could even drop this patch and just use\n>> `read` as is in 4/8. Looking from a higher level perspective, we don't care\n>> about strbuf_read_nonblocking to return after a signal without retry.\n>\n> I was actually thinking about simply teaching xread() not to worry about\n> EAGAIN, but that would probably be a regression in the \"whoops, somebody\n> gave us a non-blocking stdin!\" case.\n>\n> But yeah, I think simply using xread() as-is in strbuf_read_once (or\n> whatever it ends up being called) is OK.\n\nI was actually thinking about using {without-x}read, just the plain system call.\nDo we have any issues with that for wrapping purposes for Windows?\nThere is no technical reason to prefer xread over read in strbuf_read_once as\n* we are not nonblocking (so the EAGAIN|| EWOULDBLOCK doesn't apply)\n* we don't care about EINTR and retrying upon that signal\n* we would not care about MAX_IO_SIZE most likely (that's actually one\nof the reasons I could technically think of to prefer xread)\n\n\n> I think all of the\n> _intentionally_ non-blocking descriptors are gone in this iteration,\n> right?\n\nI think we don't even have unintentional non blocking fds here now as we\ncreate all the fds ourselves and never set the NOBLOCK flag.\n\n> So the caller of strbuf_read_once expects to have to call poll()\n> or to block. And that's what xread() does.\n\nok, I'll drop this patch and use xread there.\n\n>\n> -Peff\n"},{"id":"274474","messageId":"xmqqbn9sh4kg.fsf@gitster.mtv.corp.google.com","threadId":"40994","inReplyTo":"20151214235736.GA26133@sigill.intra.peff.net","subject":"Re: [PATCH 3/8] xread_nonblock: add functionality to read from fds without blocking","fromName":"Junio C Hamano","fromEmail":"gitster@pobox.com","sentAt":"2015-12-15T01:40:47Z","receivedAt":"2015-12-15T01:40:47Z","isPatch":true,"sender":{"key":"gitster@pobox.com","avatar":"https://avatars.githubusercontent.com/u/54884?v=4"},"body":"Jeff King writes:\n\n> Are we trying to protect ourselves against somebody _else_ giving us a\n> non-blocking descriptor? In that case we'll quietly spin and waste CPU.\n> Which isn't great, but perhaps better than returning an error.\n\nI think I said it earlier in a message upthread.\n\n> Ahh, there is a difference if the file descriptor the caller feeds\n> strbuf_read_once() happens to be marked as nonblock. read_once()\n> wants to return without doing the poll() in such a case. Even\n> though this series would not introduce any use of a nonblocking file\n> descriptor, as a general API function, [4/8] must be prepared for\n> such a future caller, hence [3/8] is needed.\n"},{"id":"274475","messageId":"20151215014456.GA28768@sigill.intra.peff.net","threadId":"40994","inReplyTo":"CAGZ79kbLHNtxcwhZz=tHpJB2XnxMeuEJBG=PmoAbcVF4Wzno2g@mail.gmail.com","subject":"Re: [PATCH 3/8] xread_nonblock: add functionality to read from fds without blocking","fromName":"Jeff King","fromEmail":"peff@peff.net","sentAt":"2015-12-15T01:44:57Z","receivedAt":"2015-12-15T01:44:57Z","isPatch":true,"sender":{"key":"peff@peff.net","avatar":"https://avatars.githubusercontent.com/u/45925?v=4"},"body":"On Mon, Dec 14, 2015 at 04:25:18PM -0800, Stefan Beller wrote:\n\n> > But yeah, I think simply using xread() as-is in strbuf_read_once (or\n> > whatever it ends up being called) is OK.\n> \n> I was actually thinking about using {without-x}read, just the plain system call.\n> Do we have any issues with that for wrapping purposes for Windows?\n> There is no technical reason to prefer xread over read in strbuf_read_once as\n> * we are not nonblocking (so the EAGAIN|| EWOULDBLOCK doesn't apply)\n> * we don't care about EINTR and retrying upon that signal\n> * we would not care about MAX_IO_SIZE most likely (that's actually one\n> of the reasons I could technically think of to prefer xread)\n\nI think you do still need to care about EINTR, or at least not barfing\nif read() returns -1. If I understand correctly, you want to do\nsomething like:\n\n while (1) {\n\tpoll(some_fds);\n\tfor (i = 0; i < nr_fds; i++) {\n\t\tif (some_fds[i].revents & POLLIN) {\n\t\t\tint r = strbuf_read_once(buf[i], some_fds[i]);\n\t\t\t/* ??? what do we do with r? */\n\t\t}\n\t}\n }\n\nIf we get EINTR from that read, it's OK for us to loop back to the\npoll() and go again.\n\nBut if we get a true error in \"r\", we'd want to know, right? That means\nwe must distinguish between EINTR and \"real\" errors (like EIO or\nsomething). We can do that here, but I think it's just as easy to do it\ninside of strbuf_read_once (by calling xread() there). It's OK not to\njump back to the poll(), because we know the data that triggered the\nPOLLIN is still waiting for us to read it.\n\nAnd we are fine with EAGAIN, too. We don't expect the sockets to be\nnon-blocking in the first place, but even if they were, we know we just\ngot POLLIN, so there should be data waiting.\n\n-Peff\n"},{"id":"274480","messageId":"566FAF61.1050704@kdbg.org","threadId":"40994","inReplyTo":"CAGZ79kbLHNtxcwhZz=tHpJB2XnxMeuEJBG=PmoAbcVF4Wzno2g@mail.gmail.com","subject":"Re: [PATCH 3/8] xread_nonblock: add functionality to read from fds without blocking","fromName":"Johannes Sixt","fromEmail":"j6t@kdbg.org","sentAt":"2015-12-15T06:12:49Z","receivedAt":"2015-12-15T06:12:49Z","isPatch":true,"sender":{"key":"j6t@kdbg.org","avatar":"https://avatars.githubusercontent.com/u/14810926?v=4"},"body":"Am 15.12.2015 um 01:25 schrieb Stefan Beller:\n> I was actually thinking about using {without-x}read, just the plain system call.\n> Do we have any issues with that for wrapping purposes for Windows?\n\nxread() limits the size being read to MAX_IO_SIZE, which is needed on \nsome systems (I think that some Windows configurations did fall into \nthis category).\n\n-- Hannes\n"}]}