Cleanup: remove trailing whitespaces at EOL

[urcu.git] / compat_futex.c

diff --git a/compat_futex.c b/compat_futex.c
index 3f1d1ef3410a91d4ae432080debcba4c6a17e387..b7f78f0b1c87a832cfb33c22e3a93845bbe7d3bb 100644 (file)
--- 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.
@@ -43,11 +54,11 @@ 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
-        * account. 
+        * account.
         */
        assert(!timeout);
        assert(!uaddr2);
@@ -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;
 }
 
 /*
@@ -88,11 +116,11 @@ 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, i;
+       int ret = 0;
 
        /*
         * Check if NULL. Don't let users expect that they are taken into
-        * account. 
+        * account.
         */
        assert(!timeout);
        assert(!uaddr2);
@@ -105,12 +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;
 }