The need for volatile is not obvious, document it.
Signed-off-by: Davidlohr Bueso <[email protected]>
---
ipc/msg.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/ipc/msg.c b/ipc/msg.c
index c2cdb5b..956cd65 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -42,9 +42,7 @@
#include <linux/uaccess.h>
#include "util.h"
-/*
- * one msg_receiver structure for each sleeping receiver:
- */
+/* one msg_receiver structure for each sleeping receiver */
struct msg_receiver {
struct list_head r_list;
struct task_struct *r_tsk;
@@ -54,6 +52,12 @@ struct msg_receiver {
long r_msgtype;
long r_maxsize;
+ /*
+ * Mark r_msg volatile so that the compiler
+ * does not try to get smart and optimize
+ * it. We rely on this for the lockless
+ * receive algorithm.
+ */
struct msg_msg *volatile r_msg;
};
--
1.8.1.4
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