Re: [PATCH v14 12/13] fsmonitor: add tests for Linux

> From: Paul Tarjan <github@paulisageek.com>
> 
> Add a smoke test that verifies the filesystem actually delivers
> inotify events to the daemon.  On some configurations (e.g.,
> overlayfs with older kernels), inotify watches succeed but events
> are never delivered.  The daemon cookie wait will time out, but
> every subsequent test would fail.  Skip the entire test file early
> when this is detected.
> 
> Add a test that exercises rapid nested directory creation to verify
> the daemon correctly handles the EEXIST race between recursive scan
> and queued inotify events.  When IN_MASK_CREATE is available and a
> directory watch is added during recursive registration, the kernel
> may also deliver a queued IN_CREATE event for the same directory.
> The second inotify_add_watch() returns EEXIST, which must be treated
> as harmless.  An earlier version of the listener crashed in this
> scenario.
> 
> Reduce --start-timeout from the default 60 seconds to 10 seconds so
> that tests fail promptly when the daemon cannot start.
> 
> Harden the test helpers to work in environments without procps
> (e.g., Fedora CI): fall back to reading /proc/$pid/stat for the
> process group ID when ps is unavailable, guard stop_git() against
> an empty pgid, and redirect stderr from kill to /dev/null to avoid
> noise when processes have already exited.
> 
> Use set -m to enable job control in the submodule-pull test so that
> the background git pull gets its own process group, preventing the
> shell wait from blocking on the daemon.  setsid() in the previous
> commit detaches the daemon itself, but the intermediate git pull
> process still needs its own process group for the test shell to
> manage it correctly.
> 
> Signed-off-by: Paul Tarjan <github@paulisageek.com>
> ---
>  t/t7527-builtin-fsmonitor.sh | 89 +++++++++++++++++++++++++++++++++---
>  1 file changed, 82 insertions(+), 7 deletions(-)
> 
> diff --git a/t/t7527-builtin-fsmonitor.sh b/t/t7527-builtin-fsmonitor.sh
> index 409cd0cd12..774da5ac60 100755
> --- a/t/t7527-builtin-fsmonitor.sh
> +++ b/t/t7527-builtin-fsmonitor.sh
> @@ -10,9 +10,58 @@ then
>  	test_done
>  fi
>  
> +# Verify that the filesystem delivers events to the daemon.
> +# On some configurations (e.g., overlayfs with older kernels),
> +# inotify watches succeed but events are never delivered.  The
> +# cookie wait will time out and the daemon logs a trace message.
> +#
> +# Use "timeout" (if available) to guard each step against hangs.
> +maybe_timeout () {
> +	if type timeout >/dev/null 2>&1
> +	then
> +		timeout "$@"
> +	else
> +		shift
> +		"$@"
> +	fi
> +}
> +verify_fsmonitor_works () {
> +	git init test_fsmonitor_smoke || return 1
> +
> +	GIT_TRACE_FSMONITOR="$PWD/smoke.trace" &&
> +	export GIT_TRACE_FSMONITOR &&
> +	maybe_timeout 30 \
> +		git -C test_fsmonitor_smoke fsmonitor--daemon start \
> +			--start-timeout=10
> +	ret=$?
> +	unset GIT_TRACE_FSMONITOR
> +	if test $ret -ne 0
> +	then
> +		rm -rf test_fsmonitor_smoke smoke.trace
> +		return 1
> +	fi
> +
> +	maybe_timeout 10 \
> +		test-tool -C test_fsmonitor_smoke fsmonitor-client query \
> +			--token 0 >/dev/null 2>&1
> +	maybe_timeout 5 \
> +		git -C test_fsmonitor_smoke fsmonitor--daemon stop 2>/dev/null
> +	! grep -q "cookie_wait timed out" "$PWD/smoke.trace" 2>/dev/null
> +	ret=$?
> +	rm -rf test_fsmonitor_smoke smoke.trace
> +	return $ret
> +}
> +
> +if ! verify_fsmonitor_works
> +then
> +	skip_all="filesystem does not deliver fsmonitor events (container/overlayfs?)"
> +	test_done
> +fi
> +
>  stop_daemon_delete_repo () {
>  	r=$1 &&
> -	test_might_fail git -C $r fsmonitor--daemon stop &&
> +	test_might_fail maybe_timeout 30 \
> +		git -C $r fsmonitor--daemon stop 2>/dev/null

>  	rm -rf $1
>  }
>  
> @@ -67,7 +116,7 @@ start_daemon () {
>  			export GIT_TEST_FSMONITOR_TOKEN
>  		fi &&
>  
> -		git $r fsmonitor--daemon start &&
> +		git $r fsmonitor--daemon start --start-timeout=10 &&
>  		git $r fsmonitor--daemon status
>  	)
>  }
> @@ -520,6 +569,28 @@ test_expect_success 'directory changes to a file' '
>  	grep "^event: dir1$" .git/trace
>  '
>  
> +test_expect_success 'rapid nested directory creation' '
> +	test_when_finished "git fsmonitor--daemon stop; rm -rf rapid" &&
> +
> +	start_daemon --tf "$PWD/.git/trace" &&
> +
> +	# Rapidly create nested directories to exercise race conditions
> +	# where directory watches may be added concurrently during
> +	# event processing and recursive scanning.
> +	for i in $(test_seq 1 20)
> +	do
> +		mkdir -p "rapid/nested/dir$i/subdir/deep" || return 1
> +	done &&
> +
> +	# Give the daemon time to process all events
> +	sleep 1 &&
> +
> +	test-tool fsmonitor-client query --token 0 &&
> +
> +	# Verify daemon is still running (did not crash)
> +	git fsmonitor--daemon status
> +'
> +
>  # The next few test cases exercise the token-resync code.  When filesystem
>  # drops events (because of filesystem velocity or because the daemon isn't
>  # polling fast enough), we need to discard the cached data (relative to the
> @@ -910,7 +981,10 @@ test_expect_success "submodule absorbgitdirs implicitly starts daemon" '
>  start_git_in_background () {
>  	git "$@" &
>  	git_pid=$!
> -	git_pgid=$(ps -o pgid= -p $git_pid)
> +	git_pgid=$(ps -o pgid= -p $git_pid 2>/dev/null ||
> +		awk '{print $5}' /proc/$git_pid/stat 2>/dev/null) &&
> +	git_pgid="${git_pgid## }" &&
> +	git_pgid="${git_pgid%% }"
>  	nr_tries_left=10
>  	while true
>  	do
> @@ -921,15 +995,16 @@ start_git_in_background () {
>  		fi
>  		sleep 1
>  		nr_tries_left=$(($nr_tries_left - 1))
> -	done >/dev/null 2>&1 &
> +	done >/dev/null 2>&1 3>&- 4>&- 5>&- 6>&- 7>&- &
>  	watchdog_pid=$!
>  	wait $git_pid
>  }
>  
>  stop_git () {
> -	while kill -0 -- -$git_pgid
> +	test -n "$git_pgid" || return 0
> +	while kill -0 -- -$git_pgid 2>/dev/null
>  	do
> -		kill -- -$git_pgid
> +		kill -- -$git_pgid 2>/dev/null
>  		sleep 1
>  	done
>  }
> @@ -944,7 +1019,7 @@ stop_watchdog () {
>  
>  test_expect_success !MINGW "submodule implicitly starts daemon by pull" '
>  	test_atexit "stop_watchdog" &&
> -	test_when_finished "stop_git; rm -rf cloned super sub" &&
> +	test_when_finished "set +m; stop_git; rm -rf cloned super sub" &&
>  
>  	create_super super &&
>  	create_sub sub &&
> -- 
> gitgitgadget
>