Subject: RE: Help needed on 2.54.0-rc0 t5301.13 looping.

From: <[email-masked]>
Date: Wed, 8 Apr 2026 11:52:34 -0400

On April 8, 2026 7:53 AM, Adrian Ratiu wrote:
>To: Jeff King <[email-masked]>; [email-masked]
>Cc: Junio C Hamano <[email-masked]>; [email-masked]
>Subject: Re: Help needed on 2.54.0-rc0 t5301.13 looping.
>
>On Wed, 08 Apr 2026, Jeff King <[email-masked]> wrote:
>> On Wed, Apr 08, 2026 at 01:20:31AM -0400, Jeff King wrote:
>>
>>> I suspect we could construct a related case that does fail on Linux
>>> without the patch above. Imagine we actually have two hooks running in
>>> parallel. The first one is fast and does not read its input, and the
>>> second one is slow. We'll get SIGPIPE writing to the first one, and then
>>> kill _both_ children. But that's wrong! There is no reason to kill the
>>> second hook, as our intent was to ignore SIGPIPE.
>>
>> This would require running hooks in parallel, which isn't implemented
>> yet for v2.54.0. But if I build on top of the ar/parallel-hooks topic,
>> then this test:
>>
>> diff --git a/t/t5401-update-hooks.sh b/t/t5401-update-hooks.sh
>> index 44ec875aef..97257763d3 100755
>> --- a/t/t5401-update-hooks.sh
>> +++ b/t/t5401-update-hooks.sh
>> @@ -139,4 +139,43 @@ test_expect_success 'pre-receive hook that forgets
to
>read its input' '
>>  	git push ./victim.git "+refs/heads/*:refs/heads/*"
>>  '
>>
>> +test_expect_success 'hooks in parallel that do not read input' '
>> +	# Add this to our $PATH to avoid having to write the whole trash
>> +	# directory into our config options, which would require quoting.
>> +	mkdir bin &&
>> +	PATH=$PWD/bin:$PATH &&
>> +
>> +	write_script bin/hook-fast <<-\EOF &&
>> +	# This hook does not read its input, so the parent process
>> +	# may see SIGPIPE if it is not ignored. It should happen
>> +	# relatively quickly.
>> +	exit 0
>> +	EOF
>> +
>> +	write_script bin/hook-slow <<-\EOF &&
>> +	# This hook is slow, so we expect it to still be running
>> +	# when the other hook has exited (and the parent has a pipe error
>> +	# writing to it).
>> +	#
>> +	# So we want to be slow enough that we expect this to happen, but
not
>> +	# so slow that the test takes forever. 1 second is probably enough
>> +	# in practice (and if it is occasionally not on a loaded system, we
>> +	# will err on the side of having the test pass).
>> +	sleep 1
>> +	exit 0
>> +	EOF
>> +
>> +
>> +	git init --bare parallel.git &&
>> +	git -C parallel.git config hook.fast.command "hook-fast" &&
>> +	git -C parallel.git config hook.fast.event pre-receive &&
>> +	git -C parallel.git config hook.fast.parallel true &&
>> +	git -C parallel.git config hook.slow.command "hook-slow" &&
>> +	git -C parallel.git config hook.slow.event pre-receive &&
>> +	git -C parallel.git config hook.slow.parallel true &&
>> +	git -C parallel.git config hook.jobs 2 &&
>> +
>> +	git push ./parallel.git "+refs/heads/*:refs/heads/*"
>> +'
>> +
>>  test_done
>>
>> fails reliably. And applying the patch I suggested earlier fixes it.
>>
>> So I think it's probably a good idea regardless, though I'm still
>> curious to see if it solves Randall's non-parallel case on NonStop.
>
>Thanks Peff for the in-depth analysis, fix and test.
>It is very much appreciated. I missed this case.
>
>I agree with your assesement: this must be fixed regardless if it also
>fixes Randall's case or not (might be a separate root cause).
>
>I would proceed like this (obviously crediting you for the fix & test):
>
>If it fixes Randall's case:
>   send a standalone bug-fix patch, then integrate the test into the
>   parallel series.
>else
>   integrate both the fix and the test into the parallel series.
>
>@Randall please let us know if the fix proposed by Peff in the other
>response works for you.

This fix, however, causes an unreported infinite loop in t5571:

expecting success of 5571.11 'sigpipe does not cause pre-push hook failure':
        test_hook --clobber pre-push <<-\EOF &&
        exit 0
        EOF
        git push parent1 "refs/heads/b/*:refs/heads/b/*"

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<and hung>