Forced commit, for previous revision.
Make state transitions of a thread on a mutex queue atomic (with respect to other threads and signal handlers). This includes: o Introduce two functions to implement atomicity with respect to other threads and signal handlers. Basically, _thread_critical_enter() locks the calling thread and blocks signals. _thread_critical_exit() unblocks signals and unlocks the thread. o Introduce two new functions: get_muncontested() locks a mutex that is not owned by another thread. get_mcontested() places a thread on a contested mutex's queue, taking care to use the _thread_critical_enter/exit functions to protect thread state. o Modify mutex_unlock_common() to also protect state transitions. In this case it needs the cooperation of mutex_queue_deq(), which must return with the thread locked and signals disabled *before* it takes the thread off the queue. Combine _pthread_mutex_lock() and _pthread_mutex_trylock() into one function: mutex_lock_common(), that can handle both cases. Its behaviour is controlled by an argument, int nonblock, which if not zero means do not attempt to acquire a contested mutex if the uncontested case fails. BTW, when I write about contested and uncontested mutexes, I'm writing about it from the application's point of view. I'm not writing about internal locking of pthread_mutex->lock, which is achieved differently. While internal mutex locking is mostly done, there's still a bit more work left in this area. Approved by: markm/mentor, re/blanket libthr Reviewed by: jeff (slightly diff. revision)
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Mike Makonnen
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479778b07f
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53555c6fe6
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=114940