WAIT_SYNC_INIT(sync,0); WAIT_SYNC_RELEASE(sync);
hanged because sync->signaled was initialised to true, and
there is no reason to invoke WAIT_SYNC_SIGNALED(sync) before
WAIT_SYNC_RELEASE(sync)
this commit initializes sync->signaled to true unless the count is zero.
Thanks George for the review and guidance.
This commit fixes a race condition discovered by @artpol84. The race
happens when a signalling thread decrements the sync count to 0 then
goes to sleep. If the waiting thread runs and detects the count == 0
before going to sleep on the condition variable it will destroy the
condition variable while the signalling thread is potentially still
processing the completion. The fix is to add a non-atomic member to
the sync structure that indicates another process is handling
completion. Since the member will only be set to false by the
initiating thread and the completing thread the variable does not need
to be protected. When destoying a condition variable the waiting
thread needs to wait until the singalling thread is finished.
Thanks to @artpol84 for tracking this down.
Fixes#1813
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>
The OPAL_ENABLE_MULTI_THREADS macro is always defined as 1. This was
causing us to always use the multi-thread path for synchronization
objects. The code has been updated to use the opal_using_threads()
function. When MPI_THREAD_MULTIPLE support is disabled at build time
(2.x only) this function is a macro evaluating to false so the
compiler will optimize out the MT-path in this case. The
OPAL_ATOMIC_ADD_32 macro has been removed and replaced by the existing
OPAL_THREAD_ADD32 macro.
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>
* Remodel the request.
Added the wait sync primitive and integrate it into the PML and MTL
infrastructure. The multi-threaded requests are now significantly
less heavy and less noisy (only the threads associated with completed
requests are signaled).
* Fix the condition to release the request.
