RE: [ANNOUNCE] Git v2.21.0-rc1 (NonStop Results)

On Fri, Feb 15, 2019 at 02:02:13PM +0100, SZEDER Gábor wrote:

quoted

I haven't yet seen that hang in the wild and couldn't reproduce it on
purpose, but there is definitely something fishy with t5562 even on
Linux and even without that perl generate_zero_bytes helper.

It won't show most of the processes run in the tests, because they are
just too fast and short-lived.  However, occasionally it does show a
stuck git process, which is shown as <defunct> in regular 'ps aux'
output:

  szeder   5722  0.0  0.0      0     0 pts/16   Z+   13:36   0:00 [git] <defunct>

Note that this is not a "proper" hang, in the sense that this process
is not stuck forever, but only for about 1 minute

This is probably because of SIGCHILD comes before "sleep". I believe this is
unrelated to the hang issue. The hang issue looks like something is wrong
with cleanu_children(), or maybe in the child which it tries to kill and wait,
not in tests.

As for this zombie issue, could be fixed with, for example, more busy wait
like the following. It may with some bigger probability miss SIGCHILD to the
first sleep because there is a bit more to do before it. But the penalty is only
1 second now, and as it still happens rarely there seems to be no visible
degradation.

--- 8< -----------
diff --git a/t/t5562/invoke-with-content-length.pl b/t/t5562/invoke-with-

content-length.pl
index 0943474af2..257e280e3b 100644

--- a/t/t5562/invoke-with-content-length.pl
+++ b/t/t5562/invoke-with-content-length.pl

@@ -29,7 +29,12 @@
 }
 print $out $body_data or die "Cannot write data: $!";

-sleep 60; # is interrupted by SIGCHLD
+my $counter = 0;
+while (not $exited and $counter < 60) {
+        sleep 1;
+        $counter = $counter + 1;
+}
+
 if (!$exited) {
         close($out);
         die "Command did not exit after reading whole body";