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[88.21.103.193]) by smtp.gmail.com with ESMTPSA id j3sm9001192wrg.72.2019.05.06.04.13.16 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Mon, 06 May 2019 04:13:16 -0700 (PDT) To: Lukas Straub , qemu-devel@nongnu.org, zhanghailiang , Paolo Bonzini , Stefan Hajnoczi References: <20190420191425.7d1dab82@luklap> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Openpgp: id=89C1E78F601EE86C867495CBA2A3FD6EDEADC0DE; url=http://pgp.mit.edu/pks/lookup?op=get&search=0xA2A3FD6EDEADC0DE Message-ID: <612f07b7-7090-8934-ce58-0a65785e9d64@redhat.com> Date: Mon, 6 May 2019 13:13:15 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190420191425.7d1dab82@luklap> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.85.221.65 Subject: Re: [Qemu-devel] [PATCH v2] net/colo-compare.c: Fix a crash in COLO Primary. X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Zhang, Chen" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Cc'ing Paolo & Stefan On 4/20/19 7:14 PM, Lukas Straub wrote: > From: Lukas Straub > 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 > --- > 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 > >