提交 00d09fdb 编写于 作者: S Stefan Hajnoczi

vl: pause vcpus before stopping iothreads

Commit dce8921b ("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: NStefan Hajnoczi <stefanha@redhat.com>
Message-id: 20180201110708.8080-1-stefanha@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
上级 bec9c64e
......@@ -4767,10 +4767,18 @@ int main(int argc, char **argv, char **envp)
main_loop();
replay_disable_events();
iothread_stop_all();
/* The ordering of the following is delicate. Stop vcpus to prevent new
* I/O requests being queued by the guest. Then stop IOThreads (this
* includes a drain operation and completes all request processing). At
* this point emulated devices are still associated with their IOThreads
* (if any) but no longer have any work to do. Only then can we close
* block devices safely because we know there is no more I/O coming.
*/
pause_all_vcpus();
iothread_stop_all();
bdrv_close_all();
res_free();
/* vhost-user must be cleaned up before chardevs. */
......
Markdown is supported
0% .
You are about to add 0 people to the discussion. Proceed with caution.
先完成此消息的编辑!
想要评论请 注册