openmv/src/omv/mutex.c
2014-08-20 21:10:43 +02:00

45 lines
748 B
C

#include <stm32f4xx.h>
#include <core_cm4.h>
#include <core_cmInstr.h>
#include "mutex.h"
void mutex_init(mutex_t *mutex)
{
mutex_unlock(mutex);
}
void mutex_lock(mutex_t *mutex)
{
volatile int locked = 0;
/* wait for mutex to be unlocked */
do {
/* attemp ex read */
while (__LDREXW(mutex) != 0);
/* attempt to lock mutex */
locked = __STREXW(1, mutex);
} while (locked != 0);
__DMB();
}
int mutex_try_lock(mutex_t *mutex)
{
volatile int locked = 1;
if (__LDREXW(mutex) != 0) {
return 0;
}
/* attempt to lock mutex */
locked = __STREXW(1, mutex);
__DMB();
return (locked == 0);
}
void mutex_unlock(mutex_t *mutex)
{
__DMB();
*mutex = 0;
}