Re: [Qemu-devel] [PATCH v2] net/colo-compare.c: Fix a crash in COLO Primary.

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

Cc'ing Paolo & Stefan

On 4/20/19 7:14 PM, Lukas Straub wrote:
> From: Lukas Straub <lukasstraub2@web.de>
> Because event_unhandled_count may be accessed concurrently, it needs
> to be protected by taking the lock. However the assert is outside the
> lock, probably causing it to read garbage and aborting Qemu erroneously.
> 
> The Bug only happens when running Qemu in COLO mode.
> 
> This Patch fixes the following bug: https://bugs.launchpad.net/qemu/+bug/1824622
> 
> Signed-off-by: Lukas Straub <lukasstraub2@web.de>
> ---
>  net/colo-compare.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/net/colo-compare.c b/net/colo-compare.c
> index bf10526f05..fcb491121b 100644
> --- a/net/colo-compare.c
> +++ b/net/colo-compare.c
> @@ -813,9 +813,8 @@ static void colo_compare_handle_event(void *opaque)
>          break;
>      }
> 
> -    assert(event_unhandled_count > 0);
> -
>      qemu_mutex_lock(&event_mtx);
> +    assert(event_unhandled_count > 0);
>      event_unhandled_count--;
>      qemu_cond_broadcast(&event_complete_cond);
>      qemu_mutex_unlock(&event_mtx);
> --
> 2.20.1
> 
>