Am 09.08.2018 um 19:35 schrieb Johannes Schindelin via GitGitGadget:
I reported a couple of times that t5552 is not passing reliably. It has now
reached next, and will no doubt infect master soon.
Turns out that it is not a Windows-specific issue, even if it occurs a lot
more often on Windows than elsewhere.
The culprit is that two processes try simultaneously to write to the same
file specified via GIT_TRACE_PACKET, and it is not well defined how that
should work, even on Linux.
Thanks for digging down to the root cause. As has been said, the
behavior of O_APPEND is well-defined under POSIX, but last time I looked
for equivalent feature on Windows, I did not find any.
Last time was when I worked around the same failure in
t5503-tagfollow.sh in my private builds:
https://github.com/j6t/git/commit/9a447a6844b50b43746d9765b3ac809e2793d742
It is basically the same as Peff suggests: log only one side of the fetch.
As this buglet looks like a recurring theme, and a proper fix is
preferable over repeated work-arounds. To me it looks like we need some
sort of locking on Windows. Unless your friends at Microsoft have an ace
in their sleeves that lets us have atomic O_APPEND the POSIX way...
-- Hannes
