[PATCH 0/4] robustifying t5504

I got a spurious test failure on t5504 while running the test suite today. This is the result of my quest through the SIGPIPE rabbit hole.

Since this is not the first time I've investigated tests failing under load, I finally broke down and wrote a helper script. It probably needs some adapting for other people's environments, but I'll share it here in case anyone is interested:

-- >8 -- #!/bin/sh

test=$1; shift test=$(cd t && echo $test*.sh) : ${GIT_STRESS_LOAD:=$(( 2 * $(grep -c ^processor /proc/cpuinfo)))} : ${GIT_STRESS_ROOT:=/var/ram/git-stress}

mkdir -p "$GIT_STRESS_ROOT" || exit 1
rm -f "$GIT_STRESS_ROOT/fail"
trap 'echo aborted >"$GIT_STRESS_ROOT/fail"' TERM INT HUP
for i in $(seq $GIT_STRESS_LOAD); do
	(
		cd t &&
		while ! test -e "$GIT_STRESS_ROOT/fail"
		do
			if ./$test \
			   --root="$GIT_STRESS_ROOT/trash-$i" \
			   -v -i >"$GIT_STRESS_ROOT/output-$i" 2>&1
			then
				echo >&2 "OK $i"
			else
				echo >&2 "FAIL $i"
				cp "$GIT_STRESS_ROOT/output-$i" "$GIT_STRESS_ROOT/fail"
			fi
		done
	) &
done
wait
cat "$GIT_STRESS_ROOT/fail"
-- 8< --

You can run it like "./stress t5504", and it will run t5504 over and over in parallel until one instance fails. Without this patch series, t5504 generally fails for me within 30 seconds or so. With it, I can run for several minutes without problems.

  [1/4]: write_or_die: handle EPIPE in async threads
  [2/4]: fetch-pack: ignore SIGPIPE in sideband demuxer
  [3/4]: test_must_fail: report number of unexpected signal
  [4/4]: t5504: handle expected output from SIGPIPE death

-Peff