coreutils-8.3: test can hang: tail-2/inotify-hash-abuse

[Jim Meyering]

Ondřej Vašík reported that coreutils-8.3's
tail-2/inotify-hash-abuse test is hanging when run via koji.
You may recall that that system uses xen with a relatively
old kernel on the host, yet quite new user-space in each guest.

At first I thought it must be hanging in one of the the until... loops,
but he added an exec 2>&9 at the beginning of that script so we could
see what's going on, and found that the wait was causing the hang.

  http://koji.fedoraproject.org/koji/getfile?taskID=1908889&name=build.log

Here are the last few lines:

  + grep '^x$' out
  + tail -qF 1 2 3 4 5 6 7 8 9
  + :
  + grep '^x$' out
  + mv 1 f
  + grep inaccessible out
  + echo a
  + dead=0
  ++ seq 10
  + for i in '$(seq 10)'
  + kill -0 544
  + grep 'has appeared;' out
  + break
  + test 0 = 0
  + kill -HUP 544
  + wait 544

That means kill -HUP is failing to kill the tail process,
so the wait hangs forever.  I confirmed that tail doesn't
do any signal manipulation itself, other than "kill" to
check whether a parent is alive when --pid=PID is used.

Ondřej confirmed that it hung also with -INT,
though the ultimate test would be to use -TERM.

Eventually someone will debug it...