Commit e653bc6b authored by Alex Bennée's avatar Alex Bennée Committed by Paolo Bonzini
Browse files

atomic.h: comment on use of atomic_read/set 



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: default avatarAlex Bennée <alex.bennee@linaro.org>
Message-Id: <20160930213106.20186-3-alex.bennee@linaro.org>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 23ea7f57

include/qemu/atomic.h

+6 −0
Original line number Diff line number Diff line
@@ -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)                              \

    ({                                                \