#include <urcu/arch.h>
#include <urcu/futex.h>
+#include <urcu/system.h>
-static pthread_mutex_t compat_futex_lock = PTHREAD_MUTEX_INITIALIZER;
-static pthread_cond_t compat_futex_cond = PTHREAD_COND_INITIALIZER;
+/*
+ * Using attribute "weak" for __urcu_compat_futex_lock and
+ * __urcu_compat_futex_cond. Those are globally visible by the entire
+ * program, even though many shared objects may have their own version.
+ * The first version that gets loaded will be used by the entire program
+ * (executable and all shared objects).
+ */
+
+__attribute__((weak))
+pthread_mutex_t __urcu_compat_futex_lock = PTHREAD_MUTEX_INITIALIZER;
+__attribute__((weak))
+pthread_cond_t __urcu_compat_futex_cond = PTHREAD_COND_INITIALIZER;
/*
* _NOT SIGNAL-SAFE_. pthread_cond is not signal-safe anyway. Though.
int compat_futex_noasync(int32_t *uaddr, int op, int32_t val,
const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
{
- int ret, gret = 0;
+ int ret = 0, lockret;
/*
* Check if NULL. Don't let users expect that they are taken into
- * account.
+ * account.
*/
assert(!timeout);
assert(!uaddr2);
*/
cmm_smp_mb();
- ret = pthread_mutex_lock(&compat_futex_lock);
- assert(!ret);
+ lockret = pthread_mutex_lock(&__urcu_compat_futex_lock);
+ if (lockret) {
+ errno = lockret;
+ ret = -1;
+ goto end;
+ }
switch (op) {
case FUTEX_WAIT:
- if (*uaddr != val)
- goto end;
- pthread_cond_wait(&compat_futex_cond, &compat_futex_lock);
+ /*
+ * Wait until *uaddr is changed to something else than "val".
+ * Comparing *uaddr content against val figures out which
+ * thread has been awakened.
+ */
+ while (CMM_LOAD_SHARED(*uaddr) == val)
+ pthread_cond_wait(&__urcu_compat_futex_cond,
+ &__urcu_compat_futex_lock);
break;
case FUTEX_WAKE:
- pthread_cond_broadcast(&compat_futex_cond);
+ /*
+ * Each wake is sending a broadcast, thus attempting wakeup of
+ * all awaiting threads, independently of their respective
+ * uaddr.
+ */
+ pthread_cond_broadcast(&__urcu_compat_futex_cond);
break;
default:
- gret = -EINVAL;
+ errno = EINVAL;
+ ret = -1;
+ }
+ lockret = pthread_mutex_unlock(&__urcu_compat_futex_lock);
+ if (lockret) {
+ errno = lockret;
+ ret = -1;
}
end:
- ret = pthread_mutex_unlock(&compat_futex_lock);
- assert(!ret);
- return gret;
+ return ret;
}
/*
int compat_futex_async(int32_t *uaddr, int op, int32_t val,
const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
{
+ int ret = 0;
+
/*
* Check if NULL. Don't let users expect that they are taken into
- * account.
+ * account.
*/
assert(!timeout);
assert(!uaddr2);
switch (op) {
case FUTEX_WAIT:
- while (*uaddr == val)
- poll(NULL, 0, 10);
+ while (CMM_LOAD_SHARED(*uaddr) == val) {
+ if (poll(NULL, 0, 10) < 0) {
+ ret = -1;
+ /* Keep poll errno. Caller handles EINTR. */
+ goto end;
+ }
+ }
break;
case FUTEX_WAKE:
break;
default:
- return -EINVAL;
+ errno = EINVAL;
+ ret = -1;
}
- return 0;
+end:
+ return ret;
}