This PR fixes a possible crash when the channel manager was freed and
there were pending messages in the message queue.
The problem was that even though the message queue already received the
WMQ_QUIT message, it was still possible to enqueue messages after this
point. This resulted in unprocessed messages in the queue when it was
deleted. The delete handler then called into channel handlers which
where aleady freed/deleted.
With this PR adding messages after WMQ_QUIT was posted to the message
queue returns an error and all channel messages are now processed before
the channels are closed/terminated.
Use InitializeCriticalSectionAndSpinCount instead of IntializeCriticalSection.
Using spin counts for critical sections of short duration enables the calling
thread to avoid the wait operation in most situations which can dramatically
improve the overall performance on multiprocessor systems.
On Linux this change has no effect because the new winpr critical section
implementation does not use the SpinCount field under Linux because the NPTL
synchronization primitives are implemented using the extremely performant
futex system calls which have this magic already built in.
However, on Mac OS X this change improved the overall performance of the
multithreaded RemoteFX decoder by 25 percent.
I've used a SpinCount of 4000 which avoided 99 percent of the wait calls.
This value is also used by Microsoft's heap manager for its per-heap
critical sections.
Note: This change requires pull request #1397 to be merged.
- Improved/completed(almost) winpr's critical section implementation
- Replaced WaitForSingleObject locking with critical sections
Note:
WaitForSingleObject should _never_ be used for granular low-contention
locks as it _always_ enters the kernel.
Just replacing WaitForSingleObject locking in Bufferpool with
EnterCriticalSection boosts the multithreaded rfx decoder
performance by almost 400% on win32.
