[Bug libitm/52526] New: libitm: stuck in futex_wait

["patrick.marlier at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52526

             Bug #: 52526
           Summary: libitm: stuck in futex_wait
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libitm
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: patrick.marlier@gmail.com
                CC: torvald@gcc.gnu.org
              Host: x86_64-unknown-linux-gnu
            Target: x86_64-unknown-linux-gnu


libitm (default configuration/4.8.0 20120307) is stuck in futex_wait with STAMP
kmeans with low contention and 8 threads.

(gdb) info threads 
  Id   Target Id         Frame 
  8    Thread 0x7ffff322b700 (LWP 24011) "kmeans" 0x0000003ecb40c14c in
pthread_barrier_wait () from /lib64/libpthread.so.0
  7    Thread 0x7ffff3a2c700 (LWP 24010) "kmeans" 0x0000003ecb40c14c in
pthread_barrier_wait () from /lib64/libpthread.so.0
  6    Thread 0x7ffff422d700 (LWP 24009) "kmeans" 0x0000003ecb40c14c in
pthread_barrier_wait () from /lib64/libpthread.so.0
  5    Thread 0x7ffff4a2e700 (LWP 24008) "kmeans" 0x0000003ecb40c14c in
pthread_barrier_wait () from /lib64/libpthread.so.0
* 4    Thread 0x7ffff522f700 (LWP 24007) "kmeans" GTM::futex_wait
(addr=0x7ffff7fdfbb8, val=1)
    at ../../../gcc-trunk/libitm/config/linux/futex.cc:49
  3    Thread 0x7ffff5a30700 (LWP 24006) "kmeans" 0x0000003ecb40c14c in
pthread_barrier_wait () from /lib64/libpthread.so.0
  2    Thread 0x7ffff6231700 (LWP 24005) "kmeans" 0x0000003ecb40c14c in
pthread_barrier_wait () from /lib64/libpthread.so.0
  1    Thread 0x7ffff73aa720 (LWP 24002) "kmeans" 0x0000003ecb40c14c in
pthread_barrier_wait () from /lib64/libpthread.so.0
(gdb) thread 5
[Switching to thread 5 (Thread 0x7ffff4a2e700 (LWP 24008))]
#0  0x0000003ecb40c14c in pthread_barrier_wait () from /lib64/libpthread.so.0
(gdb) bt
#0  0x0000003ecb40c14c in pthread_barrier_wait () from /lib64/libpthread.so.0
#1  0x0000000000403099 in threadWait ()
#2  0x0000003ecb407b41 in start_thread () from /lib64/libpthread.so.0
#3  0x0000003eca8df49d in clone () from /lib64/libc.so.6
(gdb) thread 4
[Switching to thread 4 (Thread 0x7ffff522f700 (LWP 24007))]
#0  GTM::futex_wait (addr=0x7ffff7fdfbb8, val=1) at
../../../gcc-trunk/libitm/config/linux/futex.cc:49
49        if (__builtin_expect (res == -ENOSYS, 0))
(gdb) bt
#0  GTM::futex_wait (addr=0x7ffff7fdfbb8, val=1) at
../../../gcc-trunk/libitm/config/linux/futex.cc:49
#1  0x00007ffff75cd1a4 in GTM::gtm_rwlock::read_lock (this=0x7ffff7fdfbb0,
tx=0x7fffd40008c0)
    at ../../../gcc-trunk/libitm/config/linux/rwlock.cc:76
#2  0x00007ffff75ccbfa in GTM::gtm_thread::decide_begin_dispatch
(this=0x7fffd40008c0, prop=<optimized out>)
    at ../../../gcc-trunk/libitm/retry.cc:182
#3  0x00007ffff75cc16b in GTM_begin_transaction (prop=41, jb=0x7ffff522edb0) at
../../../gcc-trunk/libitm/beginend.cc:235
#4  0x00007ffff75cd853 in _ITM_beginTransaction () at
../../../gcc-trunk/libitm/config/x86/sjlj.S:74
#5  0x00000000004021ab in work ()
#6  0x000000000040308d in threadWait ()
#7  0x0000003ecb407b41 in start_thread () from /lib64/libpthread.so.0
#8  0x0000003eca8df49d in clone () from /lib64/libc.so.6