X-Git-Url: https://git.lttng.org/?p=urcu.git;a=blobdiff_plain;f=compat_futex.c;h=6fe378f965d4407734fe16f3ffcc8ff8eb4afbb1;hp=e8d1e70f23d247437c83345ff3443be3f01cec36;hb=54fd78efce9aeddcdc7b35151ad6744b7ee629cb;hpb=2f3dd0a582f21370ed852cec76a0f97ed33416a5

diff --git a/compat_futex.c b/compat_futex.c
index e8d1e70..6fe378f 100644
--- a/compat_futex.c
+++ b/compat_futex.c
@@ -30,9 +30,20 @@
 
 #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.
@@ -43,7 +54,7 @@ static pthread_cond_t compat_futex_cond = PTHREAD_COND_INITIALIZER;
 int compat_futex_noasync(int32_t *uaddr, int op, int32_t val,
 	const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
 {
-	int ret, i, gret = 0;
+	int ret = 0, lockret;
 
 	/*
 	 * Check if NULL. Don't let users expect that they are taken into
@@ -58,25 +69,42 @@ int compat_futex_noasync(int32_t *uaddr, int op, int32_t val,
 	 */
 	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:
-		for (i = 0; i < val; i++)
-			pthread_cond_signal(&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;
 }
 
 /*
@@ -88,6 +116,8 @@ end:
 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. 
@@ -103,12 +133,20 @@ int compat_futex_async(int32_t *uaddr, int op, int32_t val,
 
 	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;
 	}
+end:
+	return ret;
 }