Arbiter.c

static TYPE PAD1 CALIGN __attribute__(( unused ));		// protect further false sharing
static VTYPE * intents, * serving;				// shared
static TYPE PAD2 CALIGN __attribute__(( unused ));		// protect further false sharing
static VTYPE arbiter_stop = 0;
static pthread_t arbiter;

// Worker id is only allowed into CS by the assignment serving[id] = 1 by the arbiter.  After CS, id sets serving[id] =
// 0.  It cannot reclaim CS until the arbiter has resumed its activity by exiting from while, and entering for.  There
// it advances to the next id, and cycles through the other workers, before it can reach id again.

static void * Worker( void * arg ) {
	TYPE id = (size_t)arg;
	uint64_t entry;

	#ifdef FAST
	unsigned int cnt = 0, oid = id;
	#endif // FAST

	NCS_DECL;

	for ( int r = 0; r < RUNS; r += 1 ) {
		RTYPE randomThreadChecksum = 0;

		for ( entry = 0; stop == 0; entry += 1 ) {
			NCS;

			intents[id] = 1;							// entry protocol
			while ( serving[id] == 0 ) Pause();			// busy wait

			randomThreadChecksum += CS( id );

			serving[id] = 0;							// exit protocol

			#ifdef FAST
			id = startpoint( cnt );						// different starting point each experiment
			cnt = cycleUp( cnt, NoStartPoints );
			#endif // FAST
		} // for

		Fai( sumOfThreadChecksums, randomThreadChecksum );

		#ifdef FAST
		id = oid;
		#endif // FAST
		entries[r][id] = entry;
		Fai( Arrived, 1 );
		while ( stop != 0 ) Pause();
		Fai( Arrived, -1 );
	} // for
	return NULL;
} // Worker

void * Arbiter( void * arg __attribute__((unused)) ) {
	int id = N;											// force cycle to start at id=0
	for ( ;; ) {
		for ( ;; ) {									// circular search => no starvation
			id = cycleUp( id, N );
		  if ( intents[id] == 1 ) break;				// want in ?
	  if ( arbiter_stop == 1 ) goto FINI;
			Pause();
		} // for
		intents[id] = 0;								// retract intent on behalf of worker
		serving[id] = 1;								// wait for exit from critical section
		while ( serving[id] == 1 ) Pause();				// busy wait
	} // for
  FINI: ;
	return NULL;
} // Arbiter

void __attribute__((noinline)) ctor() {
	intents = Allocator( sizeof(typeof(intents[0])) * N );
	serving = Allocator( sizeof(typeof(serving[0])) * N );
	for ( typeof(N) i = 0; i < N; i += 1 ) {					// initialize shared data
		intents[i] = serving[i] = 0;
	} // for

	if ( pthread_create( &arbiter, NULL, Arbiter, NULL ) != 0 ) abort();
} // ctor

void __attribute__((noinline)) dtor() {
	arbiter_stop = 1;
	if ( pthread_join( arbiter, NULL ) != 0 ) abort();

	free( (void *)serving );
	free( (void *)intents );
} // dtor

// Local Variables: //
// tab-width: 4 //
// compile-command: "gcc -Wall -Wextra -std=gnu11 -O3 -DNDEBUG -fno-reorder-functions -DPIN -DAlgorithm=Arbiter Harness.c -lpthread -lm -D`hostname` -DCFMT -DCNT=0" //
// End: //