[Openmcl-devel] odd ccl hang during gc

Osei Poku osei.poku at gmail.com
Tue Apr 14 22:54:32 PDT 2009


Unfortunately, I killed the process.  Fortunately, I did run the  
following backtraces on other a few other threads than #3.  According  
to the line numbers shown in the output below, it appears that they  
(at least the 3 threads I looked at) are all stopped at  
SEM_WAIT_FOREVER().

I guess the mystery continues...

Osei

(gdb) info threads
   15 Thread 1076246864 (LWP 14275)  0x00002b9bfc77149b in  
sem_timedwait () from /lib/libpthread.so.0
   14 Thread 1078753616 (LWP 14278)  0x00002b9bfc77149b in  
sem_timedwait () from /lib/libpthread.so.0
   13 Thread 1081260368 (LWP 14280)  0x00002b9bfc77149b in  
sem_timedwait () from /lib/libpthread.so.0
   12 Thread 1083767120 (LWP 14281)  0x00002b9bfc77149b in  
sem_timedwait () from /lib/libpthread.so.0
   11 Thread 1086273872 (LWP 14282)  0x00002b9bfc77149b in  
sem_timedwait () from /lib/libpthread.so.0
   10 Thread 1088780624 (LWP 14283)  0x00002b9bfc77149b in  
sem_timedwait () from /lib/libpthread.so.0
   9 Thread 1091287376 (LWP 24522)  0x00002b9bfc77149b in  
sem_timedwait () from /lib/libpthread.so.0
   8 Thread 1093794128 (LWP 24523)  0x00002b9bfc77149b in  
sem_timedwait () from /lib/libpthread.so.0
   7 Thread 1096841552 (LWP 24524)  0x00002b9bfc77149b in  
sem_timedwait () from /lib/libpthread.so.0
   6 Thread 1099348304 (LWP 24525)  0x00002b9bfc77149b in  
sem_timedwait () from /lib/libpthread.so.0
   5 Thread 1101855056 (LWP 28424)  0x00002b9bfc77149b in  
sem_timedwait () from /lib/libpthread.so.0
   4 Thread 1104361808 (LWP 28425)  0x00002b9bfc77149b in  
sem_timedwait () from /lib/libpthread.so.0
* 3 Thread 1106868560 (LWP 28426)  0x00002b9bfca601d8 in ?? () from / 
lib/libc.so.6
   2 Thread 1109375312 (LWP 28427)  0x00002b9bfc77149b in  
sem_timedwait () from /lib/libpthread.so.0
   1 Thread 47948961267808 (LWP 14271)  0x00002b9bfc77149b in  
sem_timedwait () from /lib/libpthread.so.0
(gdb) thread 4
[Switching to thread 4 (Thread 1104361808 (LWP 28425))]#0   
0x00002b9bfc77149b in sem_timedwait () from /lib/libpthread.so.0
(gdb) bt
#0  0x00002b9bfc77149b in sem_timedwait () from /lib/libpthread.so.0
#1  0x000000000041cc3c in sem_wait_forever (s=0x1ce0cb0) at ../ 
thread_manager.c:443
#2  0x000000000041da7f in suspend_resume_handler (signo=<value  
optimized out>, info=<value optimized out>, context=0x41d32670) at ../ 
thread_manager.c:594
#3  <signal handler called>
#4  0x00002b9bfc77149b in sem_timedwait () from /lib/libpthread.so.0
#5  0x000000000041cbdb in wait_on_semaphore (s=0x18078b0, seconds=1,  
millis=0) at ../thread_manager.c:468
#6  0x0000000000411402 in _SPffcall () at ../x86-spentry64.s:4041
#7  0x0000000000000000 in ?? ()
(gdb) thread 5
[Switching to thread 5 (Thread 1101855056 (LWP 28424))]#0   
0x00002b9bfc77149b in sem_timedwait () from /lib/libpthread.so.0
(gdb) bt
#0  0x00002b9bfc77149b in sem_timedwait () from /lib/libpthread.so.0
#1  0x000000000041cc3c in sem_wait_forever (s=0xd3e4b0) at ../ 
thread_manager.c:443
#2  0x000000000041da7f in suspend_resume_handler (signo=<value  
optimized out>, info=<value optimized out>, context=0x41ace650) at ../ 
thread_manager.c:594
#3  <signal handler called>
#4  0x00002b9bfc7727b1 in ?? () from /lib/libpthread.so.0
#5  0x0000000000411402 in _SPffcall () at ../x86-spentry64.s:4041
#6  0x0000000041aced60 in ?? ()
#7  0x00002aaaaf859e88 in ?? ()
#8  0x000000000000031a in ?? ()
#9  0x0000000041aced50 in ?? ()
#10 0x0000000000000000 in ?? ()
(gdb) thread 6
[Switching to thread 6 (Thread 1099348304 (LWP 24525))]#0   
0x00002b9bfc77149b in sem_timedwait () from /lib/libpthread.so.0
(gdb) bt
#0  0x00002b9bfc77149b in sem_timedwait () from /lib/libpthread.so.0
#1  0x000000000041cc3c in sem_wait_forever (s=0x23af950) at ../ 
thread_manager.c:443
#2  0x000000000041da7f in suspend_resume_handler (signo=<value  
optimized out>, info=<value optimized out>, context=0x4186a6c0) at ../ 
thread_manager.c:594
#3  <signal handler called>
#4  0x00002b9bfc771efb in ?? () from /lib/libpthread.so.0
#5  0x0000000000411402 in _SPffcall () at ../x86-spentry64.s:4041
#6  0x0000000000000000 in ?? ()



On Apr 15, 2009, at 1:34 AM, Gary Byers wrote:

> A bunch of threads (all but the one that GDB identifies as #3) were
> suspended by thread 3 when it ran the GC; each such suspended thread
> is waiting on a semaphore that'd be signaled/raised when the GC exits.
> It looks like the GC exited and is in the process of trying to free
> some foreign objects that were referenced by "gcable pointers"; it
> has to signal the other threads' semaphores (to wake them up) before
> it actually frees anything, since one of those threads may own a lock
> on the malloc heap.
>
> It looks like the GC thread (#3) called free(), and is waiting for
> a lock that's likely held by one of the other threads that's likely
> to still be waiting (in sem_timedwait()) to be told that it's OK
> to run.  The GC thread's already signaled the semaphores that the
> other threads are waiting on, but they don't seem to have gotten
> the message.
>
>
> It's not that unusual to see that some of the other threads are  
> apparently
> still waiting for their "resume" semaphores; it's a little unusual to
> see that they're all waiting, and I'd guess that they have been  
> waiting
> since you noticed the load average dropping to 0.
>
> If you still have the GDB attached, you might try something: make each
> other thread (other than #3) active in GDB and use 'up' to see how it
> got to sem_timedwait().  My guess is that you'd see the call to
> SEM_WAIT_FOREVER in the function 'suspend_resume_handler()' (in
> ccl/lisp-kernel/thread-manager.c) a few frames up the stack in each
> cases.  If you see that any of these threads is waiting for anything
> other than its tcr->resume semaphore, that'd be interesting.
>
> Otherwise, this is a bit of a mystery, since the whole 'suspend other
> threads on GC entry, signal their resume semaphores on GC exit'  
> routine
> happens on every GC, and has likely happened hundreds or thousands of
> times already in this session, and it's not clear what's different  
> this
> time.
>
>
>
> On Wed, 15 Apr 2009, Osei Poku wrote:
>
>> Hi,
>>
>> I was running three slime repls (9 threads total) and in each repl I
>> was running the same long running function on different inputs.   
>> After
>> a few hours of my load being about 2.8, it dropped down to 0.0.
>> Basically nothing was running, nothing responding etc.  All threads
>> are frozen.  As is confirmed by the backtrace in the main thread (see
>> below), this happened during gc which makes sense since all activity
>> stops during gc.  Not sure what else I can do to revive the process
>> but I thought it might be useful to report the issue.
>>
>> This is from CCL version 1.3-RC1-r11885M.
>>
>> Osei
>>
>> --- gdb output -----
>>
>> (gdb) info threads
>>  15 Thread 1076246864 (LWP 14275)  0x00002b9bfc77149b in
>> sem_timedwait () from /lib/libpthread.so.0
>>  14 Thread 1078753616 (LWP 14278)  0x00002b9bfc77149b in
>> sem_timedwait () from /lib/libpthread.so.0
>>  13 Thread 1081260368 (LWP 14280)  0x00002b9bfc77149b in
>> sem_timedwait () from /lib/libpthread.so.0
>>  12 Thread 1083767120 (LWP 14281)  0x00002b9bfc77149b in
>> sem_timedwait () from /lib/libpthread.so.0
>>  11 Thread 1086273872 (LWP 14282)  0x00002b9bfc77149b in
>> sem_timedwait () from /lib/libpthread.so.0
>>  10 Thread 1088780624 (LWP 14283)  0x00002b9bfc77149b in
>> sem_timedwait () from /lib/libpthread.so.0
>>  9 Thread 1091287376 (LWP 24522)  0x00002b9bfc77149b in
>> sem_timedwait () from /lib/libpthread.so.0
>>  8 Thread 1093794128 (LWP 24523)  0x00002b9bfc77149b in
>> sem_timedwait () from /lib/libpthread.so.0
>>  7 Thread 1096841552 (LWP 24524)  0x00002b9bfc77149b in
>> sem_timedwait () from /lib/libpthread.so.0
>>  6 Thread 1099348304 (LWP 24525)  0x00002b9bfc77149b in
>> sem_timedwait () from /lib/libpthread.so.0
>>  5 Thread 1101855056 (LWP 28424)  0x00002b9bfc77149b in
>> sem_timedwait () from /lib/libpthread.so.0
>>  4 Thread 1104361808 (LWP 28425)  0x00002b9bfc77149b in
>> sem_timedwait () from /lib/libpthread.so.0
>>  3 Thread 1106868560 (LWP 28426)  0x00002b9bfca601d8 in ?? () from /
>> lib/libc.so.6
>>  2 Thread 1109375312 (LWP 28427)  0x00002b9bfc77149b in
>> sem_timedwait () from /lib/libpthread.so.0
>>  1 Thread 47948961267808 (LWP 14271)  0x00002b9bfc77149b in
>> sem_timedwait () from /lib/libpthread.so.0
>> (gdb) thread
>> [Current thread is 0 (LWP 14271)]
>> (gdb) thread 2
>> [Switching to thread 2 (Thread 1109375312 (LWP 28427))]#0
>> 0x00002b9bfc77149b in sem_timedwait () from /lib/libpthread.so.0
>> (gdb) thread 3
>> [Switching to thread 3 (Thread 1106868560 (LWP 28426))]#0
>> 0x00002b9bfca601d8 in ?? () from /lib/libc.so.6
>> (gdb) bt
>> #0  0x00002b9bfca601d8 in ?? () from /lib/libc.so.6
>> #1  0x00002b9bfc9f6662 in ?? () from /lib/libc.so.6
>> #2  0x00002b9bfc9f56f1 in free () from /lib/libc.so.6
>> #3  0x000000000041ca69 in destroy_semaphore (s=0x300055b0bc08) at ../
>> thread_manager.c:724
>> #4  0x0000000000414caa in reap_gcable_ptrs () at ../gc-common.c:746
>> #5  0x00000000004157bd in gc (tcr=0x41f977b0, param=<value optimized
>> out>) at ../gc-common.c:1331
>> #6  0x00000000004196db in gc_from_tcr (tcr=0x2b9bfccd6980, param=0)
>> at ../x86-exceptions.c:2786
>> #7  0x000000000041abe1 in gc_like_from_xp (xp=<value optimized out>,
>> fun=0x4196b0 <gc_from_tcr>, param=0) at ../x86-exceptions.c:2743
>> #8  0x000000000041ac3e in gc_from_xp (xp=0x2b9bfccd6980,
>> param=25576416) at ../x86-exceptions.c:2798
>> #9  0x000000000041ad67 in allocate_object (xp=0x41f966f0,
>> bytes_needed=6352096, disp_from_allocptr=6352083, tcr=0x41f977b0)
>> at ../x86-exceptions.c:145
>> #10 0x000000000041adce in handle_alloc_trap (xp=0x41f966f0,
>> tcr=0x41f977b0) at ../x86-exceptions.c:572
>> #11 0x000000000041b5ce in handle_exception (signum=<value optimized
>> out>, info=0x41f96aa0, context=0x41f966f0, tcr=0x8000000000000000,
>> old_valence=-1) at ../x86-exceptions.c:1060
>> #12 0x000000000041b698 in signal_handler (signum=11, info=0x41f96aa0,
>> context=0x41f966f0) at ../x86-exceptions.c:1330
>> #13 <signal handler called>
>> #14 0x000000000041054a in _SPmisc_alloc () at ../x86-spentry64.s:2840
>> #15 0x000030004036943c in ?? ()
>> #16 0x000000000060ecd0 in ?? ()
>> #17 0x0000000000000000 in ?? ()
>> (gdb) up
>> #1  0x00002b9bfc9f6662 in ?? () from /lib/libc.so.6
>> (gdb) up
>> #2  0x00002b9bfc9f56f1 in free () from /lib/libc.so.6
>> (gdb) up
>> #3  0x000000000041ca69 in destroy_semaphore (s=0x300055b0bc08) at ../
>> thread_manager.c:724
>> 724         free(*s);
>> (gdb) list
>> 719     destroy_semaphore(void **s)
>> 720     {
>> 721       if (*s) {
>> 722     #ifdef USE_POSIX_SEMAPHORES
>> 723         sem_destroy((sem_t *)*s);
>> 724         free(*s);
>> 725     #endif
>> 726     #ifdef USE_MACH_SEMAPHORES
>> 727         semaphore_destroy(mach_task_self(),((semaphore_t) 
>> (natural)
>> *s));
>> 728     #endif
>> (gdb) up
>> #4  0x0000000000414caa in reap_gcable_ptrs () at ../gc-common.c:746
>> 746               destroy_semaphore((void**)&(x->address));
>> (gdb) list
>> 741             case xmacptr_flag_rwlock:
>> 742               rwlock_destroy((rwlock *)ptr_from_lispobj(ptr));
>> 743               break;
>> 744
>> 745             case xmacptr_flag_semaphore:
>> 746               destroy_semaphore((void**)&(x->address));
>> 747               break;
>> 748
>> 749             default:
>> 750               if ((flag >= xmacptr_flag_user_first) &&
>> (gdb)
>>
>> _______________________________________________
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>> Openmcl-devel at clozure.com
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>>
>>




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