jack1/macosx/pThreadUtilities.c

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/* pThreadUtilities.c */

#define THREAD_SET_PRIORITY			0
#define THREAD_SCHEDULED_PRIORITY		1

#include <mach/thread_policy.h>
#include <mach/thread_act.h>
#include <CoreAudio/HostTime.h>

#include "pThreadUtilities.h"


UInt32 _getThreadPriority (pthread_t inThread, int inWhichPriority);


void setThreadToPriority(pthread_t inThread, UInt32 inPriority, Boolean inIsFixed, UInt64 inHALIOProcCycleDurationInNanoseconds)
{
	if (inPriority == 96)
	{
            // REAL-TIME / TIME-CONSTRAINT THREAD
            thread_time_constraint_policy_data_t	theTCPolicy;
            UInt64					theComputeQuanta;
            UInt64					thePeriod;
            UInt64					thePeriodNanos;
		
            thePeriodNanos = inHALIOProcCycleDurationInNanoseconds;
            theComputeQuanta = AudioConvertNanosToHostTime ( thePeriodNanos * 0.15 );
            thePeriod = AudioConvertNanosToHostTime (thePeriodNanos);
        
            theTCPolicy.period = thePeriod;
            theTCPolicy.computation = theComputeQuanta;
            theTCPolicy.constraint = thePeriod;
            theTCPolicy.preemptible = true;
            thread_policy_set (pthread_mach_thread_np(inThread), THREAD_TIME_CONSTRAINT_POLICY, (thread_policy_t)&theTCPolicy, THREAD_TIME_CONSTRAINT_POLICY_COUNT);
	} else {
            // OTHER THREADS
            thread_extended_policy_data_t		theFixedPolicy;
            thread_precedence_policy_data_t		thePrecedencePolicy;
            SInt32					relativePriority;
        
            // [1] SET FIXED / NOT FIXED
            theFixedPolicy.timeshare = !inIsFixed;
            thread_policy_set (pthread_mach_thread_np(inThread), THREAD_EXTENDED_POLICY, (thread_policy_t)&theFixedPolicy, THREAD_EXTENDED_POLICY_COUNT);
        
            // [2] SET PRECEDENCE
            // N.B.: We expect that if thread A created thread B, and the program wishes to change
            // the priority of thread B, then the call to change the priority of thread B must be
            // made by thread A.
            // This assumption allows us to use pthread_self() to correctly calculate the priority
            // of the feeder thread (since precedency policy's importance is relative to the
            // spawning thread's priority.)
            relativePriority = inPriority - getThreadSetPriority (pthread_self());
        
            thePrecedencePolicy.importance = relativePriority;
            thread_policy_set (pthread_mach_thread_np(inThread), THREAD_PRECEDENCE_POLICY, (thread_policy_t)&thePrecedencePolicy, THREAD_PRECEDENCE_POLICY_COUNT);
	}
}

// returns the thread's priority as it was last set by the API
UInt32 getThreadSetPriority(pthread_t inThread)
{
    return _getThreadPriority (inThread, THREAD_SET_PRIORITY);
}

// returns the thread's priority as it was last scheduled by the Kernel
UInt32 getThreadScheduledPriority(pthread_t inThread)
{
    return _getThreadPriority (inThread, THREAD_SCHEDULED_PRIORITY);
}

UInt32 _getThreadPriority(pthread_t inThread, int inWhichPriority)
{
    thread_basic_info_data_t	threadInfo;
    policy_info_data_t		thePolicyInfo;
    unsigned int		count;
    
    // get basic info
    count = THREAD_BASIC_INFO_COUNT;
    thread_info (pthread_mach_thread_np (inThread), THREAD_BASIC_INFO, (thread_info_t)&threadInfo, &count);

    switch (threadInfo.policy) {
        case POLICY_TIMESHARE:
            count = POLICY_TIMESHARE_INFO_COUNT;
            thread_info(pthread_mach_thread_np (inThread), THREAD_SCHED_TIMESHARE_INFO, (thread_info_t)&(thePolicyInfo.ts), &count);
            if (inWhichPriority == THREAD_SCHEDULED_PRIORITY) {
                return thePolicyInfo.ts.cur_priority;
            } else {
                return thePolicyInfo.ts.base_priority;
            }
        break;
        
        case POLICY_FIFO:
            count = POLICY_FIFO_INFO_COUNT;
            thread_info(pthread_mach_thread_np (inThread), THREAD_SCHED_FIFO_INFO, (thread_info_t)&(thePolicyInfo.fifo), &count);
            if ( (thePolicyInfo.fifo.depressed) && (inWhichPriority == THREAD_SCHEDULED_PRIORITY) ) {
                return thePolicyInfo.fifo.depress_priority;
            }
            return thePolicyInfo.fifo.base_priority;
        break;
        
        case POLICY_RR:
            count = POLICY_RR_INFO_COUNT;
            thread_info(pthread_mach_thread_np (inThread), THREAD_SCHED_RR_INFO, (thread_info_t)&(thePolicyInfo.rr), &count);
            if ( (thePolicyInfo.rr.depressed) && (inWhichPriority == THREAD_SCHEDULED_PRIORITY) ) {
                return thePolicyInfo.rr.depress_priority;
            }
            return thePolicyInfo.rr.base_priority;
        break;
    }
    
    return 0;
}