Introduction to Concurrency in Programming Languages

High-Level Language Constructs 95

Listing 5.1: Explicit locking to protect a critical section in C with POSIX

threads.

int sharedA , sha redB ;

p t h r e a d m u t e x t swapMutex ;

void ThreadBod y ( void * thread id ) {

int tmp ;

p t h r e a d m u t e x l o c k (& swapMutex );

tmp = sharedA ;

sharedA = shar edB + 4;

sharedB = shar edA - 2;

p t h r e a d m u t e x u n l o c k (& swapMutex );

pthread_ e xit ( NULL );

}

int main ( int argc , char ** argv ) {

/* ... */

p t h r e a d m u t e x i n i t (& swapMutex , NULL );

for ( t =0; t < N UM_THREADS ; t ++) {

rc = pthread_create (& threads [t ] , NULL ,

ThreadBody , ( void *) t );

if ( rc ) { /* ... */ }

}

for