/* 
 * Readers-writers solution with weak reader priority
 * From Courtois et al, CACM, 1971.
*/
#include "csapp.h"

/* $begin reader1 */
/* Global variables */
int readcnt;    /* Initially = 0 */
sem_t mutex, w; /* Both initially = 1 */

void reader(void) 
{
    while (1) {
	P(&mutex);
	readcnt++;
	if (readcnt == 1) /* First in */
	    P(&w);          
	V(&mutex);          

	/* Critical section */
	/* Reading happens  */

	P(&mutex);
	readcnt--;
	if (readcnt == 0) /* Last out */
	    V(&w);
	V(&mutex);
    }
}
/* $end reader1 */

/* $begin writer1 */




void writer(void) 
{
    while (1) {
	P(&w);

	/* Critical section */
	/* Writing happens  */ 

	V(&w);
    }
}
/* $end writer1 */