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Description of problem:
There seems to be a race condition in electric fence and pthreads. I have a
large multithreaded application that, during shutdown, has many threads
exiting and many calls to "free" all at once. About 1 in 5 shutdowns, two
threads get deadlocked. gdb reveals that one thread is as follows:

(gdb) where
#0  0x400cf8a5 in __sigsuspend (set=0x41b228ec)
    at ../sysdeps/unix/sysv/linux/sigsuspend.c:45
#1  0x400920d9 in __pthread_wait_for_restart_signal (self=0x41b22c00)
    at pthread.c:934
#2  0x400930ac in __new_sem_wait (sem=0x400a173c) at restart.h:34
#3  0x4009f179 in lock () from /usr/lib/libefence.so.0
#4  0x4009fa10 in free () from /usr/lib/libefence.so.0
#5  0x40092bf3 in __pthread_destroy_specifics () at specific.c:165
#6  0x4008f2d7 in pthread_exit (retval=0x0) at join.c:37
#7  0x4008fc05 in pthread_start_thread (arg=0x41b22c00) at manager.c:265

And another is:

(gdb) where
#0  0x400cf8a5 in __sigsuspend (set=0x4132260c)
    at ../sysdeps/unix/sysv/linux/sigsuspend.c:45
#1  0x400920d9 in __pthread_wait_for_restart_signal (self=0x41322c00)
    at pthread.c:934
#2  0x400930ac in __new_sem_wait (sem=0x400a173c) at restart.h:34
#3  0x4009f179 in lock () from /usr/lib/libefence.so.0
#4  0x4009fa10 in free () from /usr/lib/libefence.so.0
#5  0x08085064 in wms_free (deadbuf=0x45d1cff0) at wms.c:109

(wms_free() is my function that calls free). It seems that all other
threads exit fine, these two are stuck, so I'm guessing some kind of bad
interaction when a thread is exiting just as another is freeing memory. If
you have trouble reproducing this, let me know.

Version-Release number of selected component (if applicable):
ElectricFence-2.2.2-7

How reproducible:
Sometimes

Steps to Reproduce:
1.Uhhh...run my large non-free multithreaded server
2.exit
3.OK so this is hard for you to reproduce. If a glance at the code doesn't
make the bug obvious, let me know, I'll see if I can write a small program
to reproduce. Now I feel really lazy telling you to look at the code
instead of me. Really, I would, I'm trying to put together a release in the
next 2 hours and I don't have time. Maybe later today I'll see what I can
find if I can get this release done.
	

Actual Results:  Two threads got deadlocked.

Expected Results:  Threads should have just plain exited.

Additional info:

Would be wonderful to get efence working with threads. I think I have a
problem accessing memory after freeing, I can't find it, but it happens
very rarely (like once every month the server is running) so I need to be
able to run production server with efence, and that isn't possible when the
thread of this shutdown problem is there.