We are seeing a deadlock when making use of the interprocess_semaphore.
In our case we have two running threads where the first thread is stuck waiting at a timed_wait() call while the second thread is stuck at a post() call.
Also, a symptom we are seeing is that the lock value is set to 1 before both threads try to acquire the lock -- we think this is why the
Derek Kivi wrote: threads
get stuck in the lock calls.
We are running 1.36 at the moment. Have there been any fixes in 1.37 or 1.38 that might help us to avoid this problem?
I don't remember any fix but I can't be sure. Thanks for the report, but I'm afraid this will be difficult to catch :-(
Thanks, Derek
Regards,
Ion
Hi Ion, Thanks for your reply. A co-worker has looked into this a bit more and believes that he has found the source of the problem. He thinks that this is a bug in interprocess_condition::do_timed_wait(). Here is his description to me: ---------------------------------- In the code there's one hole where it doesn't unlock the m_enter_mut mutex before it leaves do_wait. This is in the following code: //Notification occurred, we will lock the checking interprocess_mutex so that //if a notify_one notification occurs, only one thread can exit //--------------------------------------------------------------- InternalLock lock; if(tout_enabled){ InternalLock dummy(m_check_mut, abs_time); lock = detail::move_impl(dummy); } else{ InternalLock dummy(m_check_mut); lock = detail::move_impl(dummy); } if(!lock) { return false; } The return false; is the problem here. It's at the point where m_check_mut can't be locked that this routine exits without unlocking m_enter_mut, and thus causing the deadlock. Trivially, this can be fixed by executing m_enter_mut.unlock(); before returning. ---------------------------------- Ion, do you think that it is okay to add an m_enter_mut.unlock() call before returning? Will this cause some other problem in another part of the code? Thanks for your help, Derek -- Derek Kivi Senior Software Developer QuIC Financial Technologies Inc. Office: +1 403 210 8282 Mobile: +1 403 863 5204 derek.kivi@quic.com Risk. Managed. www.quic.com Confidentiality Notice: The information transmitted is intended only for the person(s) or entity(ies) to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination, or other use of, or taking of any action in reliance upon this information by persons or entities other than the intended recipient is prohibited. If you received this email in error, please contact the sender and delete the email and any related material from any computer. ver. QuIC 0707