From 4486e89c219c0d1b9bd8dfa0b1dd5b0d51ff2268 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Wed, 7 Mar 2018 14:42:05 +0000 Subject: vl: introduce vm_shutdown() Commit 00d09fdbbae5f7864ce754913efc84c12fdf9f1a ("vl: pause vcpus before stopping iothreads") and commit dce8921b2baaf95974af8176406881872067adfa ("iothread: Stop threads before main() quits") tried to work around the fact that emulation was still active during termination by stopping iothreads. They suffer from race conditions: 1. virtio_scsi_handle_cmd_vq() racing with iothread_stop_all() hits the virtio_scsi_ctx_check() assertion failure because the BDS AioContext has been modified by iothread_stop_all(). 2. Guest vq kick racing with main loop termination leaves a readable ioeventfd that is handled by the next aio_poll() when external clients are enabled again, resulting in unwanted emulation activity. This patch obsoletes those commits by fully disabling emulation activity when vcpus are stopped. Use the new vm_shutdown() function instead of pause_all_vcpus() so that vm change state handlers are invoked too. Virtio devices will now stop their ioeventfds, preventing further emulation activity after vm_stop(). Note that vm_stop(RUN_STATE_SHUTDOWN) cannot be used because it emits a QMP STOP event that may affect existing clients. It is no longer necessary to call replay_disable_events() directly since vm_shutdown() does so already. Drop iothread_stop_all() since it is no longer used. Cc: Fam Zheng Cc: Kevin Wolf Signed-off-by: Stefan Hajnoczi Reviewed-by: Fam Zheng Acked-by: Paolo Bonzini Message-id: 20180307144205.20619-5-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi --- vl.c | 15 ++++----------- 1 file changed, 4 insertions(+), 11 deletions(-) (limited to 'vl.c') diff --git a/vl.c b/vl.c index dae986b352..3ef04ce991 100644 --- a/vl.c +++ b/vl.c @@ -4722,17 +4722,10 @@ int main(int argc, char **argv, char **envp) os_setup_post(); main_loop(); - replay_disable_events(); - - /* 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(); + + /* No more vcpu or device emulation activity beyond this point */ + vm_shutdown(); + bdrv_close_all(); res_free(); -- cgit v1.2.1