Re: [Qemu-block] [Qemu-devel] [PATCH] throttle-groups: update tg->any_timer_armed[] on detach

[Michael Roth]

Quoting Stefan Hajnoczi (2017-09-19 10:50:25)
> Clear tg->any_timer_armed[] when throttling timers are destroy during
> AioContext attach/detach.  Failure to do so causes throttling to hang
> because we believe the timer is already scheduled!
> 
> The following was broken at least since QEMU 2.10.0 with -drive
> iops=100:
> 
>   $ dd if=/dev/zero of=/dev/vdb oflag=direct count=1000
>   (qemu) stop
>   (qemu) cont
>   ...I/O is stuck...
> 
> Reported-by: Yongxue Hong <address@hidden>
> Signed-off-by: Stefan Hajnoczi <address@hidden>

FYI: this patch has been tagged for stable 2.10.1, but is not yet
upstream. Patch freeze for 2.10.1 is September 27th.

> ---
>  block/throttle-groups.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/block/throttle-groups.c b/block/throttle-groups.c
> index 6ba992c8d7..2bfd03faa0 100644
> --- a/block/throttle-groups.c
> +++ b/block/throttle-groups.c
> @@ -592,7 +592,20 @@ void 
> throttle_group_attach_aio_context(ThrottleGroupMember *tgm,
>  void throttle_group_detach_aio_context(ThrottleGroupMember *tgm)
>  {
>      ThrottleTimers *tt = &tgm->throttle_timers;
> +    ThrottleGroup *tg = container_of(tgm->throttle_state, ThrottleGroup, ts);
> +
>      throttle_timers_detach_aio_context(tt);
> +
> +    /* Forget about these timers, they have been destroyed */
> +    qemu_mutex_lock(&tg->lock);
> +    if (tg->tokens[0] == tgm) {
> +        tg->any_timer_armed[0] = false;
> +    }
> +    if (tg->tokens[1] == tgm) {
> +        tg->any_timer_armed[1] = false;
> +    }
> +    qemu_mutex_unlock(&tg->lock);
> +
>      tgm->aio_context = NULL;
>  }
> 
> -- 
> 2.13.5
> 
>