On Wed, Sep 15, 2021 at 01:24:52PM -0400, Jeff King wrote: > On Wed, Sep 15, 2021 at 01:13:25PM -0400, Jeff King wrote: > > > I think this test may be racy. I saw a strange failure from it in CI: > > > > https://github.com/peff/git/runs/3605506649?check_suite_focus=true#step:5:6734 > > > > I can't reproduce the problem locally with "--stress", but the failure > > there is on macOS (and likewise, a nearby run failed with a timeout just > > for macOS, which could be caused by a racy deadlock). > > Ah, I just wasn't trying hard enough. Using --run=1,190 lets it run a > lot more tightly, and I got a failure pretty quickly. Here's the fix (on > top of ps/update-ref-batch-flush). > > -- >8 -- > Subject: [PATCH] t1400: avoid SIGPIPE race condition on fifo > > t1400.190 sometimes fails or even hangs because of the way it uses > fifos. Our goal is to interactively read and write lines from > update-ref, so we have two fifos, in and out. We open a descriptor > connected to "in" and redirect output to that, so that update-ref does > not see EOF as it would if we opened and closed it for each "echo" call. > > But we don't do the same for the output. This leads to a race where our > "read response <out" has not yet opened the fifo, but update-ref tries > to write to it and gets SIGPIPE. This can result in the test failing, or > worse, hanging as we wait forever for somebody to write to the pipe. > > This is the same proble we fixed in 4783e7ea83 (t0008: avoid SIGPIPE Type: "proble" -> "problem". > race condition on fifo, 2013-07-12), and we can fix it the same way, by > opening a second long-running descriptor. > > Before this patch, running: > > ./t1400-update-ref.sh --run=1,190 --stress > > failed or hung within a few dozen iterations. After it, I ran it for > several hundred without problems. > > Signed-off-by: Jeff King <peff@xxxxxxxx> > --- > t/t1400-update-ref.sh | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/t/t1400-update-ref.sh b/t/t1400-update-ref.sh > index 1e754e258f..0d4f73acaa 100755 > --- a/t/t1400-update-ref.sh > +++ b/t/t1400-update-ref.sh > @@ -1603,19 +1603,21 @@ test_expect_success PIPE 'transaction flushes status updates' ' > (git update-ref --stdin <in >out &) && > > exec 9>in && > + exec 8<out && > test_when_finished "exec 9>&-" && > + test_when_finished "exec 8<&-" && > > echo "start" >&9 && > echo "start: ok" >expected && > - read line <out && > + read line <&8 && > echo "$line" >actual && > test_cmp expected actual && > > echo "create refs/heads/flush $A" >&9 && > > echo prepare >&9 && > echo "prepare: ok" >expected && > - read line <out && > + read line <&8 && > echo "$line" >actual && > test_cmp expected actual && > > @@ -1625,7 +1627,7 @@ test_expect_success PIPE 'transaction flushes status updates' ' > > echo commit >&9 && > echo "commit: ok" >expected && > - read line <out && > + read line <&8 && > echo "$line" >actual && > test_cmp expected actual > ' > -- > 2.33.0.917.g33ebf6a5f6 > Thanks a lot for digging and fixing my test. The patch looks good to me. Patrick
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