Re: [PATCH 1/1] monitor: don't wake up qmp_dispatcher_co coroutine upon cleanup

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 2/5/25 23:47, andrey.drobyshev@virtuozzo.com wrote:
> From: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
> 
> Since the commit 3e6bed61 ("monitor: cleanup detection of qmp_dispatcher_co
> shutting down"), coroutine pointer qmp_dispatcher_co is set to NULL upon
> cleanup.  If a QMP command is sent after monitor_cleanup() (e.g. after
> shutdown), this may lead to SEGFAULT on aio_co_wake(NULL).
> 
> As mentioned in the comment inside monitor_cleanup(), the intention is to
> allow incoming requests while shutting down, but simply leave them
> without any response.  Let's do exactly that, and if qmp_dispatcher_co
> coroutine pointer has already been set to NULL, let's simply skip the
> aio_co_wake() part.
> 

Cc: qemu-stable@nongnu.org

> Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
> ---
>   monitor/qmp.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/monitor/qmp.c b/monitor/qmp.c
> index 2f46cf9e49..cb99a12d94 100644
> --- a/monitor/qmp.c
> +++ b/monitor/qmp.c
> @@ -356,7 +356,8 @@ void qmp_dispatcher_co_wake(void)
>       /* Write request before reading qmp_dispatcher_co_busy.  */
>       smp_mb__before_rmw();
>   
> -    if (!qatomic_xchg(&qmp_dispatcher_co_busy, true)) {
> +    if (!qatomic_xchg(&qmp_dispatcher_co_busy, true) &&
> +            qatomic_read(&qmp_dispatcher_co)) {
>           aio_co_wake(qmp_dispatcher_co);
>       }
>   }