From: Johannes Schindelin via GitGitGadget Date: Wed, 10 Nov 2021 11:09:10 GMT Subject: [PATCH] simple-ipc: work around issues with Cygwin's Unix socket emulation Message-ID: From: Johannes Schindelin Cygwin emulates Unix sockets by writing files with custom contents and then marking them as system files. The tricky problem is that while the file is written and its `system` bit is set, it is still identified as a file. This caused test failures when Git is too fast looking for the Unix sockets and then complains that there is a plain file in the way. Let's work around this by adding a delayed retry loop, specifically for Cygwin. Signed-off-by: Johannes Schindelin --- simple-ipc: work around issues with Cygwin's Unix socket emulation Adam Dinwoodie reported problems running the simple-ipc tests on Cygwin [https://lore.kernel.org/git/20211104194619.GA12886@dinwoodie.org]. This patch works around the underlying problem, which is rooted in Cygwin's implementation details. With this patch, I could not reproduce the problem, even with sh t0052-simple-ipc.sh --stress-limit=30. As per Junio's encouragement [https://lore.kernel.org/git/xmqqee7ozyx4.fsf@gitster.g], I am submitting this still in the -rc phase, hoping that it will make it into v2.34.0 final. Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1074%2Fdscho%2Fcygwin-vs-simple-ipc-workaround-v1 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1074/dscho/cygwin-vs-simple-ipc-workaround-v1 Pull-Request: https://github.com/gitgitgadget/git/pull/1074 compat/simple-ipc/ipc-unix-socket.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/compat/simple-ipc/ipc-unix-socket.c b/compat/simple-ipc/ipc-unix-socket.c index 4e28857a0a1..28a79289d4f 100644 --- a/compat/simple-ipc/ipc-unix-socket.c +++ b/compat/simple-ipc/ipc-unix-socket.c @@ -35,6 +35,28 @@ enum ipc_active_state ipc_get_active_state(const char *path) } } +#ifdef __CYGWIN__ + /* + * Cygwin emulates Unix sockets by writing special-crafted files whose + * `system` bit is set. + * + * If we are too fast, Cygwin might still be in the process of marking + * the underlying file as a system file. Until then, we will not see a + * Unix socket here, but a plain file instead. Just in case that this + * is happening, wait a little and try again. + */ + { + static const int delay[] = { 1, 10, 20, 40, -1 }; + int i; + + for (i = 0; S_ISREG(st.st_mode) && delay[i] > 0; i++) { + sleep_millisec(delay[i]); + if (lstat(path, &st) == -1) + return IPC_STATE__INVALID_PATH; + } + } +#endif + /* also complain if a plain file is in the way */ if ((st.st_mode & S_IFMT) != S_IFSOCK) return IPC_STATE__INVALID_PATH; base-commit: 6c220937e2b26d85920bf2d38ff2464a0d57fd6b -- gitgitgadget