[PATCH] t5400: avoid concurrent writes into a trace file
- From
Jeff King <peff@peff.net>
- Date
- May 18, 2017, 05:02 UTC
- Message-ID
- <20170518050209.dezna5tillvlbwgw@sigill.intra.peff.net>
- In-Reply-To
- <83b6c8d3-2787-995a-a4e5-e6a437c53e89@kdbg.org>
On Wed, May 17, 2017 at 08:41:01PM +0200, Johannes Sixt wrote:
Show 7 quoted lines
> Am 17.05.2017 um 07:44 schrieb Jeff King: > > I wonder if there's a way we could convince the trace for the two > > programs to go to separate locations. We don't care about receive-pack's > > trace at all. So maybe: > > This works. Below it is with a commit message. I'm unsure about the > sign-off procedure, though.
Thanks for testing. I actually wrote one in preparation, but I like yours a little better.
I'll repost here with my signoff and a cc to Junio, since the earlier subject line was less likely to grab attention. This goes on top of jk/alternate-ref-optim.
-- >8 -- Subject: t5400: avoid concurrent writes into a trace file
One test in t5400 examines the packet exchange between git-push and git-receive-pack. The latter inherits the GIT_TRACE_PACKET environment variable, so that both processes dump trace data into the same file concurrently. This should not be a problem because the trace file is opened with O_APPEND.
On Windows, however, O_APPEND is not atomic as it should be: it is emulated as lseek(SEEK_END) followed by write(). For this reason, the test is unreliable: it can happen that one process overwrites a line that was just written by the other process. As a consequence, the test sometimes does not find one or another line that is expected (and it is also successful occasionally).
The test case is actually only interested in the output of git-push. To ensure that only git-push writes to the trace file, override the receive-pack command such that it does not even open the trace file.
Reported-by: Johannes Sixt <j6t@kdbg.org> Signed-off-by: Jeff King <peff@peff.net> --- t/t5400-send-pack.sh | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/t/t5400-send-pack.sh b/t/t5400-send-pack.sh index 3331e0f53..d375d7110 100755 --- a/t/t5400-send-pack.sh +++ b/t/t5400-send-pack.sh @@ -288,7 +288,10 @@ test_expect_success 'receive-pack de-dupes .have lines' ' $shared .have EOF - GIT_TRACE_PACKET=$(pwd)/trace git push fork HEAD:foo && + GIT_TRACE_PACKET=$(pwd)/trace \ + git push \ + --receive-pack="unset GIT_TRACE_PACKET; git-receive-pack" \ + fork HEAD:foo && extract_ref_advertisement <trace >refs && test_cmp expect refs '
-- 2.13.0.219.g63f6bc368