pthread_lock

[june.tune.sea@gmail.com (ishare)]

On Tue, Mar 12, 2013 at 06:18:02PM +0530, Prabhu nath wrote:
> I guess we should not mix mutex and condition variable. Both have their own
> respective semantics.
> *mutex* is used to serialize access to a shared resource among competing
> threads.
> *condition variable* is used to notify a* state change* of a resource to
> the interested thread.
> 
> In case of condition variable there is provision to explicitly notify a
> single thread(pthread_cond_signal) or all the threads waiting on a
> condition (or a state change) (pthread_cond_broadcast)
> 
> Question was on pthread_mutex_unlock() that whether this function
> invocation will trigger the movement of all the threads in the wait queue
> to the ready queue.
  
  After pthread_mutex_unlock() is called , the mutex is release , then ,which stuff 
  will reshcedule the threads in the waitqueue ?

  If do pthread_cond_signal() after each pthread_mutex_unlock() ,does it raise up the performence  ? 
 
  thanks!







> If all the threads are of equal priority, then the first thread waiting for
> the lock will be put to READY queue.
> If there are variable priority threads waiting for the lock, then the
> thread with highest priority would be woken up