Bug 68992

Summary:	valgrind stuck in umtx state before exit
Product:	Base System	Reporter:	Emil Mikulic <g3c7a531>
Component:	kern	Assignee:	freebsd-bugs (Nobody) <bugs>
Status:	Closed FIXED
Severity:	Affects Only Me
Priority:	Normal
Version:	5.2-CURRENT
Hardware:	Any
OS:	Any

Description Emil Mikulic 2004-07-13 15:50:20 UTC

I'm inclined to think this is a bug in the kernel rather than valgrind
because this wasn't happening with a kernel from a few weeks ago.

I'm running a 5-CURRENT world and kernel as of 13 July 2004 at 12:40
UTC.  valgrind hangs before exit, after printing leak information.  top
says it's stuck in the umtx state:

  PID USERNAME PRI NICE   SIZE    RES STATE    TIME   WCPU    CPU COMMAND
  516 emikulic  95    0   335M  7176K umtx     0:00  0.00%  0.00% valgrind

DDB's ps says:

  pid   proc     uarea   uid  ppid  pgrp  flag   stat  wmesg    wchan  cmd
  516 c18928ac d83f0000 1000   458   516 0004002 [SLPQ umtx 0xc17fa000][SLP] valgrind

I can't kill it with SIGTERM, SIGINT, or SIGQUIT, and I can't suspend
it.  It dies on SIGKILL though.

I get the same behaviour with both valgrind-327 and
valgrind-snapshot-337.

How-To-Repeat: 	valgrind --tool=memcheck ls

Comment 1 Emil Mikulic 2004-07-14 08:04:13 UTC

I've found three commits (through binary search with cvsup) after which
the umtx hang happens:

http://lists.freebsd.org/pipermail/cvs-src/2004-July/026488.html
http://lists.freebsd.org/pipermail/cvs-src/2004-July/026489.html
http://lists.freebsd.org/pipermail/cvs-src/2004-July/026490.html

In terms of time:

src-sys date=2004.07.02.00.38.00 # no hang
src-sys date=2004.07.02.00.41.00 # hang

Comment 2 Emil Mikulic 2004-07-14 09:32:21 UTC

It turns out that valgrind uses the "contested" flag (which was
changed), hard-coding it as a magic number instead of using the (now
non-existant) UMTX_CONTESTED macro.

Please close this PR.  I'm sorry about the noise (and also about
doubting the kernel)

Meanwhile, the following patch works for me:
--- valgrind-current-337-orig/coregrind/vg_proxylwp.c	Fri Apr  9 22:23:30 2004
+++ valgrind-current-337/coregrind/vg_proxylwp.c	Wed Jul 14 18:27:03 2004
@@ -28,9 +28,13 @@
    The GNU General Public License is contained in the file COPYING.
 */
 
-
 #include "vg_include.h"
 
+#ifndef UMTX_CONTESTED
+# include <sys/limits.h>
+# define UMTX_CONTESTED LONG_MIN /* XXX bad */
+#endif
+
 /* We need our own copy of VG_(do_syscall)() to handle a special
    race-condition.  If we've got signals unblocked, and we take a
    signal in the gap either just before or after the syscall, we may
@@ -588,7 +592,7 @@
 
 #if __FreeBSD__ == 5
    VG_(do_syscall)(__NR__umtx_lock, &px->mutex);
-   px->mutex.u_owner |= 1;	/* XXX set contested bit for simplicity */
+   px->mutex.u_owner |= UMTX_CONTESTED;	/* XXX set contested bit for simplicity */
    VG_(do_syscall)(__NR_thr_self, &px->lwp);
 #endif
 #if __FreeBSD__ == 4

Comment 3 Simon L. B. Nielsen freebsd_committer

2004-07-14 10:25:08 UTC

State Changed
From-To: open->closed

Close at submitters request. 

BTW. the FreeBSD kernel isn't bug free so it's ok to doubt it 
sometimes :-).