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mutex2.c
93 lines (79 loc) · 2.02 KB
/
mutex2.c
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#include <stdlib.h>
#include <pthread.h>
#define NHASH 29
#define HASH(fp) (((unisgned long) fp) % NHASH)
struct foo *fh[NHASH];
pthread_mutex_t hashlock = PTHREAD_MUTEX_INIIALIZER;
struct foo{
int f_count; /* protected by hashlock*/
pthread_mutex_t f_lock;
struct foo * f_next; /* protected by hashlock */
int f_id;
/* ... more stuff here ... */
};
struct foo *
foo_alloc(void) /* allocate the object */
{
struct foo *fp;
int idx;
if((fp = malloc(sizeof(struct foo))) != NULL){
fp->f_count = 1;
if(pthread_mutex_init(&fp->f_lock,NULL) !=0){
free(fp);
return(NULL);
}
idx = HASH(fp);
pthread_mutex_lock(&hashlock);
fp->f_next = fh[idx];
fh[idx] = fp->f_next;
pthread_mutex_lock(&fp->f_lock);
pthread_mutex_unlock(&hashlock);
/* ... continue initiallization ... */
}
return (fp);
}
void foo_hold(struct foo *fp) /* add a reference to the object */
{
pthread_mutex_lock(&hashlock);
fp->f_count++;
pthread_mutex_unlock(&hashlock);
}
struct foo *
foo_find(int id) /* find a existing object */
{
struct foo *fp;
int idx;
idx = HASH(fp);
pthread_mutex_lock(&hashlock);
for(fp = fh[idx]; fp != NULL; fp = fp->f_next){
if(fp->f_id == id){
fp-> f_count++;
break;
}
}
pthread_mutex_unlock(&hashlock);
return(fp);
}
void
foo_rele (struct foo *fp) /* release a reference to the object */
{
struct foo * tfp;
int idx;
pthread_mutex_lock(&hashlock);
if(--fp ->f_count == 0){ /* last reference, remove from list */
idx = HASH(fp);
tfp = fh[idx];
if(tfp == fp){
fh[idx] = fp->f_next;
}else{
while(tfp->f_next !=fp)
tfp = tfp -> f_next;
tfp->f_next = fp->f_next;
}
pthread_mutex_unlock(&hashlock);
pthread_mutex_destroy(&fp -> f_lock);
free(fp);
} else{
pthread_mutex_unlock(&hashlock);
}
}