From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58759) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1egY09-0002ft-S3 for qemu-devel@nongnu.org; Tue, 30 Jan 2018 10:39:16 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1egY08-0007ug-Uf for qemu-devel@nongnu.org; Tue, 30 Jan 2018 10:39:13 -0500 From: Stefan Hajnoczi Date: Tue, 30 Jan 2018 15:38:35 +0000 Message-Id: <20180130153835.7372-1-stefanha@redhat.com> Subject: [Qemu-devel] [PATCH] vl: pause vcpus before stopping iothreads List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, Kevin Wolf , Fam Zheng , Stefan Hajnoczi Commit dce8921b2baaf95974af8176406881872067adfa ("iothread: Stop threads before main() quits") introduced iothread_stop_all() to avoid the following virtio-scsi assertion failure: assert(blk_get_aio_context(d->conf.blk) == s->ctx); Back then the assertion failed because when bdrv_close_all() made d->conf.blk NULL, blk_get_aio_context() returned the global AioContext instead of s->ctx. The same assertion can still fail today when vcpus submit new I/O requests after iothread_stop_all() has moved the BDS to the global AioContext. This patch hardens the iothread_stop_all() approach by pausing vcpus before calling iothread_stop_all(). Note that the assertion failure is a race condition. It is not possible to reproduce it reliably. Signed-off-by: Stefan Hajnoczi --- vl.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/vl.c b/vl.c index e517a8d995..011f22ae20 100644 --- a/vl.c +++ b/vl.c @@ -4765,10 +4765,10 @@ int main(int argc, char **argv, char **envp) os_setup_post(); main_loop(); + replay_disable_events(); + pause_all_vcpus(); iothread_stop_all(); - - pause_all_vcpus(); bdrv_close_all(); res_free(); -- 2.14.3