Re: [PATCH 7/8] qemu-coroutine-lock: add smp_mb__after_rmw()

[Richard Henderson]

On 3/3/23 09:19, Paolo Bonzini wrote:
> mutex->from_push and mutex->handoff in qemu-coroutine-lock implement
> the familiar pattern:
>
>     write a                                  write b
>     smp_mb()                                 smp_mb()
>     read b                                   read a
>
> The memory barrier is required by the C memory model even after a
> SEQ_CST read-modify-write operation such as QSLIST_INSERT_HEAD_ATOMIC.
> Add it and avoid the unclear qatomic_mb_read() operation.
>
> Signed-off-by: Paolo Bonzini<pbonzini@redhat.com>
> ---
>   util/qemu-coroutine-lock.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~