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

[Lukas Straub]

On Sat, 20 Apr 2019 19:14:25 +0200
Lukas Straub <address@hidden> wrote:

> From: Lukas Straub <address@hidden>
> 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 <address@hidden>
> ---
>  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);

Ping.

Regards,
Lukas Straub