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	lock.c - 9base - revived minimalist port of Plan 9 userland to Unix
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	---
	lock.c (873B)
	---
	1 #include <u.h>
	2 #include <unistd.h>
	3 #include <sys/time.h>
	4 #include <sched.h>
	5 #include <errno.h>
	6 #include <libc.h>
	7
	8 static pthread_mutex_t initmutex = PTHREAD_MUTEX_INITIALIZER;
	9
	10 static void
	11 lockinit(Lock *lk)
	12 {
	13 pthread_mutexattr_t attr;
	14
	15 pthread_mutex_lock(&initmutex);
	16 if(lk->init == 0){
	17 pthread_mutexattr_init(&attr);
	18 pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_NORMAL);
	19 pthread_mutex_init(&lk->mutex, &attr);
	20 pthread_mutexattr_destroy(&attr);
	21 lk->init = 1;
	22 }
	23 pthread_mutex_unlock(&initmutex);
	24 }
	25
	26 void
	27 lock(Lock *lk)
	28 {
	29 if(!lk->init)
	30 lockinit(lk);
	31 if(pthread_mutex_lock(&lk->mutex) != 0)
	32 abort();
	33 }
	34
	35 int
	36 canlock(Lock *lk)
	37 {
	38 int r;
	39
	40 if(!lk->init)
	41 lockinit(lk);
	42 r = pthread_mutex_trylock(&lk->mutex);
	43 if(r == 0)
	44 return 1;
	45 if(r == EBUSY)
	46 return 0;
	47 abort();
	48 }
	49
	50 void
	51 unlock(Lock *lk)
	52 {
	53 if(pthread_mutex_unlock(&lk->mutex) != 0)
	54 abort();
	55 }