From 512c90c90ebdc0d77891bbef7265e9d40f812d02 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Fri, 3 Mar 2023 11:00:43 +0100 Subject: [PATCH] qemu-coroutine: remove qatomic_mb_read() Replace with an explicit barrier and a comment. Reviewed-by: Stefan Hajnoczi Signed-off-by: Paolo Bonzini --- util/qemu-coroutine.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/util/qemu-coroutine.c b/util/qemu-coroutine.c index 8494523692..17a88f6505 100644 --- a/util/qemu-coroutine.c +++ b/util/qemu-coroutine.c @@ -127,9 +127,13 @@ void qemu_aio_coroutine_enter(AioContext *ctx, Coroutine *co) Coroutine *to = QSIMPLEQ_FIRST(&pending); CoroutineAction ret; - /* Cannot rely on the read barrier for to in aio_co_wake(), as there are - * callers outside of aio_co_wake() */ - const char *scheduled = qatomic_mb_read(&to->scheduled); + /* + * Read to before to->scheduled; pairs with qatomic_cmpxchg in + * qemu_co_sleep(), aio_co_schedule() etc. + */ + smp_read_barrier_depends(); + + const char *scheduled = qatomic_read(&to->scheduled); QSIMPLEQ_REMOVE_HEAD(&pending, co_queue_next);