http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50175
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |jakub at gcc dot gnu.org,
| |rth at gcc dot gnu.org
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-08-24
14:55:18 UTC ---
If this is about bar->arrived writes, then I don't see any races.
During the lifetime of a barrier, in the first phase arrived is incremented by
each thread, guarded by bar->mutex1 lock. The threads then unlock bar->mutex1
lock, except for the last thread which keeps it locked and decrements
bar->arrived again, then, still with bar->mutex1 locked wakes up all the other
threads which then either atomically, or guarded with bar->mutex2 lock,
decrement bar->arrived again. The last of those threads then posts to
bar->sem2
semaphore on which the thread holding bar->mutex1 is waiting before unlocking
that lock. Thus, I don't see how the first phase (where bar->arrived
adjustments are done guarded with bar->mutex1 lock) can overlap with the second
phase (where it is decremented atomically or with mutex2). Not even the second
phase with following first phase. Thus I think valgrind is wrong about this.
CCing rth as author...
