Synchronizing Attributes

Problem

	Thread 1		Thread 2		Thread 3
      High Priority	      Med Priority	      Low Priority
	 sleep()		 sleep()
						      P_M_L(mutex);
							......
       (Wakes up)
      P_M_L(mutex);
							......
			       (Wakes up)
				while(1);




Priority Mutexes

int pthread_mutexattr_setprotocol(pthread_mutex_attr *attr, int protocol);


int pthread_mutexattr_getprotocol(pthread_mutex_attr *attr, int * protocol);

PTHREAD_PRIO_INHERIT, PTHREAD_PRIO_PROTECT



PTHREAD_PRIO_INHERIT


	
 Boosts the priority of the current owner of the mutex when
	a higher priority thread blocks waiting for the lock.
	
 Used for low contention locks.




PTHREAD_PRIO_PROTECT


	
 Boosts the priority of a thread when it becomes owner of the mutex.
	
 Priority should be set to the highest priority thread that
		will lock the mutex.
	
 Used for short lived high contention locks.
	
 High contention long lived locks should be replaced with more locks


int pthread_mutexattr_setprioceiling(pthread_mutex_attr *attr, int prio);


int pthread_mutexattr_getprioceiling(pthread_mutex_attr *attr, int * prio);














Prepared by 

Chris Provenzano (proven@mit.edu)