#include "librace.h"
#include "stdatomic.h"
-
#define RW_LOCK_BIAS 0x00100000
#define WRITE_LOCK_CMP RW_LOCK_BIAS
/** Example implementation of linux rw lock along with 2 thread test
* driver... */
-
typedef union {
atomic_int lock;
} rwlock_t;
static inline void read_lock(rwlock_t *rw)
{
- int currentvalue=atomic_fetch_sub_explicit(&rw->lock, 1, memory_order_acquire);
- while (currentvalue<0) {
+ int priorvalue=atomic_fetch_sub_explicit(&rw->lock, 1, memory_order_acquire);
+ while (priorvalue<=0) {
atomic_fetch_add_explicit(&rw->lock, 1, memory_order_relaxed);
do {
- currentvalue=atomic_load_explicit(&rw->lock, memory_order_relaxed);
- } while(currentvalue<=0);
- currentvalue=atomic_fetch_sub_explicit(&rw->lock, 1, memory_order_acquire);
+ priorvalue=atomic_load_explicit(&rw->lock, memory_order_relaxed);
+ } while(priorvalue<=0);
+ priorvalue=atomic_fetch_sub_explicit(&rw->lock, 1, memory_order_acquire);
}
}
static inline void write_lock(rwlock_t *rw)
{
- int currentvalue=atomic_fetch_sub_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_acquire);
- while (currentvalue!=0) {
+ int priorvalue=atomic_fetch_sub_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_acquire);
+ while (priorvalue!=RW_LOCK_BIAS) {
atomic_fetch_add_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_relaxed);
do {
- currentvalue=atomic_load_explicit(&rw->lock, memory_order_relaxed);
- } while(currentvalue!=RW_LOCK_BIAS);
- currentvalue=atomic_fetch_sub_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_acquire);
+ priorvalue=atomic_load_explicit(&rw->lock, memory_order_relaxed);
+ } while(priorvalue!=RW_LOCK_BIAS);
+ priorvalue=atomic_fetch_sub_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_acquire);
}
}
static inline int read_trylock(rwlock_t *rw)
{
- int currentvalue=atomic_fetch_sub_explicit(&rw->lock, 1, memory_order_acquire);
- if (currentvalue>=0)
+ int priorvalue=atomic_fetch_sub_explicit(&rw->lock, 1, memory_order_acquire);
+ if (priorvalue>0)
return 1;
-
+
atomic_fetch_add_explicit(&rw->lock, 1, memory_order_relaxed);
return 0;
}
static inline int write_trylock(rwlock_t *rw)
{
- int currentvalue=atomic_fetch_sub_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_acquire);
- if (currentvalue>=0)
+ int priorvalue=atomic_fetch_sub_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_acquire);
+ if (priorvalue==RW_LOCK_BIAS)
return 1;
-
+
atomic_fetch_add_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_relaxed);
return 0;
}
thrd_create(&t1, (thrd_start_t)&a, NULL);
thrd_create(&t2, (thrd_start_t)&a, NULL);
-
+
thrd_join(t1);
thrd_join(t2);
}