qemu-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Qemu-devel] [PATCH v3 02/15] atomic.h: comment on use of atomic_read/se


From: Alex Bennée
Subject: [Qemu-devel] [PATCH v3 02/15] atomic.h: comment on use of atomic_read/set
Date: Fri, 30 Sep 2016 22:30:53 +0100

Add some notes on the use of the relaxed atomic access helpers and their
importance for defined behaviour in C11's multi-threaded memory model.

Signed-off-by: Alex Bennée <address@hidden>
---
 include/qemu/atomic.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h
index c493f89..c4f6950 100644
--- a/include/qemu/atomic.h
+++ b/include/qemu/atomic.h
@@ -92,6 +92,12 @@
 /* Weak atomic operations prevent the compiler moving other
  * loads/stores past the atomic operation load/store. However there is
  * no explicit memory barrier for the processor.
+ *
+ * The C11 memory model says that variables that are accessed from
+ * different threads should at least be done with __ATOMIC_RELAXED
+ * primitives or the result is undefined. Generally this has little to
+ * no effect on the generated code but not using the atomic primitives
+ * will get flagged by sanitizers as a violation.
  */
 #define atomic_read(ptr)                              \
     ({                                                \
-- 
2.9.3




reply via email to

[Prev in Thread] Current Thread [Next in Thread]