iothread: Stop threads before main() quits

Right after main_loop ends, we release various things but keep iothread
alive. The latter is not prepared to the sudden change of resources.

Specifically, after bdrv_close_all(), virtio-scsi dataplane get a
surprise at the empty BlockBackend:

(gdb) bt
    at /usr/src/debug/qemu-2.6.0/hw/scsi/virtio-scsi.c:543
    at /usr/src/debug/qemu-2.6.0/hw/scsi/virtio-scsi.c:577

It is because the d->conf.blk->root is set to NULL, then
blk_get_aio_context() returns qemu_aio_context, whereas s->ctx is still
pointing to the iothread:

    hw/scsi/virtio-scsi.c:543:

    if (s->dataplane_started) {
        assert(blk_get_aio_context(d->conf.blk) == s->ctx);
    }

To fix this, let's stop iothreads before doing bdrv_close_all().

Cc: qemu-stable@nongnu.org
Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1473326931-9699-1-git-send-email-famz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit dce8921b2baaf95974af8176406881872067adfa)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/vl.c b/vl.c
index b3c80d5077..3414e1a694 100644
--- a/vl.c
+++ b/vl.c
@@ -121,6 +121,7 @@ int main(int argc, char **argv)
 #include "crypto/init.h"
 #include "sysemu/replay.h"
 #include "qapi/qmp/qerror.h"
+#include "sysemu/iothread.h"
 
 #define MAX_VIRTIO_CONSOLES 1
 #define MAX_SCLP_CONSOLES 1
@@ -4603,6 +4604,7 @@ int main(int argc, char **argv, char **envp)
     trace_init_vcpu_events();
     main_loop();
     replay_disable_events();
+    iothread_stop_all();
 
     bdrv_close_all();
     pause_all_vcpus();