Re: [Qemu-block] [PATCH v3 for-2.11 2/4] coroutine: abort if we try to schedule or enter a pending coroutine

[Stefan Hajnoczi]

On Tue, Nov 21, 2017 at 10:38:51AM -0500, Jeff Cody wrote:
> diff --git a/util/qemu-coroutine.c b/util/qemu-coroutine.c
> index d6095c1..9e4ed43 100644
> --- a/util/qemu-coroutine.c
> +++ b/util/qemu-coroutine.c
> @@ -107,8 +107,21 @@ void qemu_aio_coroutine_enter(AioContext *ctx, Coroutine 
> *co)
>      Coroutine *self = qemu_coroutine_self();
>      CoroutineAction ret;
>  
> +    /* Prior read of co protected by callers - e.g., aio_co_wake */
> +    const char *scheduled = atomic_read(&co->scheduled);

Consider: user code -> qemu_coroutine_enter() ->
qemu_aio_coroutine_enter().  Unlike the
aio_co_wake() code path, there is no read barrier here.

I think atomic_mb_read() is needed to guarantee the thread sees the
latest value.

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