[PATCH 3/5] Documentation: add caveats about I/O buffering for check-{attr,ignore}
- From
Adam Spiers <git@adamspiers.org>
- Date
- Apr 11, 2013, 01:59 UTC
- Message-ID
- <1365645575-11428-3-git-send-email-git@adamspiers.org>
- In-Reply-To
- <1365645575-11428-1-git-send-email-git@adamspiers.org>
check-attr and check-ignore have the potential to deadlock callers which do not read back the output in real-time. For example, if a caller writes N paths out and then reads N lines back in, it risks becoming blocked on write() to check-*, and check-* is blocked on write back to the caller. Somebody has to buffer; the pipe buffers provide some leeway, but they are limited.
Thanks to Peff for pointing this out:
http://article.gmane.org/gmane.comp.version-control.git/220534
Signed-off-by: Adam Spiers <git@adamspiers.org> --- Documentation/git-check-attr.txt | 5 +++++ Documentation/git-check-ignore.txt | 5 +++++ Documentation/git.txt | 16 +++++++++------- 3 files changed, 19 insertions(+), 7 deletions(-)
diff --git a/Documentation/git-check-attr.txt b/Documentation/git-check-attr.txt index 5abdbaa..a7be80d 100644 --- a/Documentation/git-check-attr.txt +++ b/Documentation/git-check-attr.txt @@ -56,6 +56,11 @@ being queried and <info> can be either: 'set';; when the attribute is defined as true. <value>;; when a value has been assigned to the attribute. +Buffering happens as documented under the `GIT_FLUSH` option in +linkgit:git[1]. The caller is responsible for avoiding deadlocks +caused by overfilling an input buffer or reading from an empty output +buffer. + EXAMPLES -------- diff --git a/Documentation/git-check-ignore.txt b/Documentation/git-check-ignore.txt index 854e4d0..4014d28 100644 --- a/Documentation/git-check-ignore.txt +++ b/Documentation/git-check-ignore.txt @@ -66,6 +66,11 @@ are also used instead of colons and hard tabs: <source> <NULL> <linenum> <NULL> <pattern> <NULL> <pathname> <NULL> +Buffering happens as documented under the `GIT_FLUSH` option in +linkgit:git[1]. The caller is responsible for avoiding deadlocks +caused by overfilling an input buffer or reading from an empty output +buffer. + EXIT STATUS ----------- diff --git a/Documentation/git.txt b/Documentation/git.txt index 6a875f2..eecdb15 100644 --- a/Documentation/git.txt +++ b/Documentation/git.txt @@ -808,13 +808,15 @@ for further details. 'GIT_FLUSH':: If this environment variable is set to "1", then commands such - as 'git blame' (in incremental mode), 'git rev-list', 'git log', - and 'git whatchanged' will force a flush of the output stream - after each commit-oriented record have been flushed. If this - variable is set to "0", the output of these commands will be done - using completely buffered I/O. If this environment variable is - not set, Git will choose buffered or record-oriented flushing - based on whether stdout appears to be redirected to a file or not. + as 'git blame' (in incremental mode), 'git rev-list', 'git + log', 'git check-attr', 'git check-ignore', and 'git + whatchanged' will force a flush of the output stream after + each commit-oriented record have been flushed. If this + variable is set to "0", the output of these commands will be + done using completely buffered I/O. If this environment + variable is not set, Git will choose buffered or + record-oriented flushing based on whether stdout appears to be + redirected to a file or not. 'GIT_TRACE':: If this variable is set to "1", "2" or "true" (comparison
-- 1.8.2.1.347.g37e0606