From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Mon, 6 Jul 2015 19:01:22 +0000 (-0400)
Subject: Fix: compat_futex.c: *uaddr should be read as volatile
X-Git-Tag: v0.9.0~48
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=f4fe930941ad7e73ca2064c8be1abc31626ec50b;p=userspace-rcu.git

Fix: compat_futex.c: *uaddr should be read as volatile

Ensure that a volatile read is used when reading *uaddr in the
compatibility implementation for sys_futex FUTEX_WAIT.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/compat_futex.c b/compat_futex.c
index 9a08624..6ec0b39 100644
--- a/compat_futex.c
+++ b/compat_futex.c
@@ -30,6 +30,7 @@
 
 #include <urcu/arch.h>
 #include <urcu/futex.h>
+#include <urcu/system.h>
 
 /*
  * Using attribute "weak" for __urcu_compat_futex_lock and
@@ -77,7 +78,7 @@ int compat_futex_noasync(int32_t *uaddr, int op, int32_t val,
 		 * Comparing *uaddr content against val figures out which
 		 * thread has been awakened.
 		 */
-		while (*uaddr == val)
+		while (CMM_LOAD_SHARED(*uaddr) == val)
 			pthread_cond_wait(&__urcu_compat_futex_cond,
 				&__urcu_compat_futex_lock);
 		break;
@@ -121,7 +122,7 @@ int compat_futex_async(int32_t *uaddr, int op, int32_t val,
 
 	switch (op) {
 	case FUTEX_WAIT:
-		while (*uaddr == val)
+		while (CMM_LOAD_SHARED(*uaddr) == val)
 			poll(NULL, 0, 10);
 		break;
 	case FUTEX_WAKE: