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<base href="https://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - PowerPC Potential Deadlock with omp_set_lock"
href="https://llvm.org/bugs/show_bug.cgi?id=26199">26199</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>PowerPC Potential Deadlock with omp_set_lock
</td>
</tr>
<tr>
<th>Product</th>
<td>OpenMP
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Runtime Library
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>matt.davis@pgroup.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=15660" name="attach_15660" title="Runtime deadlock">attachment 15660</a> <a href="attachment.cgi?id=15660&action=edit" title="Runtime deadlock">[details]</a></span>
Runtime deadlock
Hello,
I think that I might have found a potential trigger for deadlock within the
kmpc runtime. I can successfully recreate this in linux on an OpenPOWER
machine, using both the Intel version of the omp runtime and the one provided
at openmp.llvm.org via svn.
Intel: libomp_20151009_oss.tgz, and built using 'make compiler=gcc'.
LLVM: <a href="http://llvm.org/svn/llvm-project/openmp/trunk">http://llvm.org/svn/llvm-project/openmp/trunk</a> with revision: r257078
built using cmake and only setting the cc and cxx cmake macros.
This test case calls an omp_set_lock/omp_unset_lock in the body of a 'parallel
for'. When running with around 6 threads, the test will occasionally
(frequently but not consistently) get stuck: in calling kmpc_set_lock and the
other calling kmpc_unset_lock. Both of the aforementioned threads are stuck in
kmp_wait_yield_4. Since I cannot get this sample to trigger consistently, I do
have success wrapping the executable in a shell for-loop:
for i in `seq 200`; do ./a.out; done
System: Linux 3.16.0-44-generic #59~14.04.1-Ubuntu SMP Tue Jul 7 15:08:52 UTC
2015 ppc64le ppc64le ppc64le GNU/Linux
Debugger Dump:
(gdb) info threads
Id Target Id Frame
7 Thread 0x3fff7b18f1a0 (LWP 129534) "a.out" 0x00003fff7b43eb74 in
__pthread_cond_timedwait (cond=0x3fff7b51d180 <__kmp_wait_cv>,
mutex=0x3fff7b51d100 <__kmp_wait_mx>, abstime=0x3fff7b18e600) at
pthread_cond_timedwait.c:199
6 Thread 0x3fff7b15f2a0 (LWP 129535) "a.out" 0x00003fff7b43e6f0 in
__pthread_cond_wait (cond=0x10039585b00, mutex=0x10039585b80) at
pthread_cond_wait.c:187
5 Thread 0x3fff7b04f3a0 (LWP 129536) "a.out" 0x00003fff7b43e6f0 in
__pthread_cond_wait (cond=0x10039588e80, mutex=0x10039588f00) at
pthread_cond_wait.c:187
4 Thread 0x3fff7af3f4a0 (LWP 129537) "a.out" 0x00003fff7b4f238c in
__kmp_wait_yield_4 () from libomp.so
3 Thread 0x3fff7ae2f5a0 (LWP 129538) "a.out" 0x00003fff7b43e6f0 in
__pthread_cond_wait (cond=0x1003958f600, mutex=0x1003958f680) at
pthread_cond_wait.c:187
2 Thread 0x3fff7ad1f6a0 (LWP 129539) "a.out" 0x00003fff7b4f2354 in
__kmp_wait_yield_4 () from libomp.so
* 1 Thread 0x3fff7b524850 (LWP 129533) "a.out" 0x00003fff7b43e6f0 in
__pthread_cond_wait (cond=0x10039582c80, mutex=0x10039582d00) at
pthread_cond_wait.c:187
Thread 2:
#0 0x00003fff7b4f2354 in __kmp_wait_yield_4 () from libomp.so
#1 0x00003fff7b4f3584 in __kmp_release_queuing_lock () from libomp.so
#2 0x00003fff7b4f3084 in __kmp_unset_indirect_lock(unsigned int*, int) () from
libomp.so
#3 0x00003fff7b4af178 in __kmpc_unset_lock () from libomp.so
#4 0x00003fff7b4deef4 in <a href="mailto:omp_unset_lock@OMP_3.0">omp_unset_lock@OMP_3.0</a> () from libomp.so
Thread 4:
#0 0x00003fff7b4f238c in __kmp_wait_yield_4 () from libomp.so
#1 0x00003fff7b4f7040 in __kmp_acquire_queuing_lock () from libomp.so
#2 0x00003fff7b4f2ff4 in __kmp_set_indirect_lock(unsigned int*, int) () from
libomp.so
#3 0x00003fff7b4af098 in __kmpc_set_lock () from libomp.so
#4 0x00003fff7b4dee34 in <a href="mailto:omp_set_lock@OMP_3.0">omp_set_lock@OMP_3.0</a> () from libomp.so
I hope that my attached sample will provide you with enough information to help
diagnose this. If not, please let me know.
-Matt</pre>
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