qemu-thread: handle spurious futex_wait wakeups

Signed-off-by: NEmilio G. Cota <cota@braap.org>
Message-Id: <1440375847-17603-12-git-send-email-cota@braap.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

util/qemu-thread-posix.c

@@ -298,7 +298,16 @@ static inline void futex_wake(QemuEvent *ev, int n)
 
 static inline void futex_wait(QemuEvent *ev, unsigned val)
 {
-    futex(ev, FUTEX_WAIT, (int) val, NULL, NULL, 0);
+    while (futex(ev, FUTEX_WAIT, (int) val, NULL, NULL, 0)) {
+        switch (errno) {
+        case EWOULDBLOCK:
+            return;
+        case EINTR:
+            break; /* get out of switch and retry */
+        default:
+            abort();
+        }
+    }
 }
 #else
 static inline void futex_wake(QemuEvent *ev, int n)