qemu/include/sysemu/iothread.h
Stefan Hajnoczi 4486e89c21 vl: introduce vm_shutdown()
Commit 00d09fdbba ("vl: pause vcpus before
stopping iothreads") and commit dce8921b2b
("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 <famz@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 20180307144205.20619-5-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2018-03-08 17:38:51 +00:00

60 lines
1.5 KiB
C

/*
* Event loop thread
*
* Copyright Red Hat Inc., 2013
*
* Authors:
* Stefan Hajnoczi <stefanha@redhat.com>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*
*/
#ifndef IOTHREAD_H
#define IOTHREAD_H
#include "block/aio.h"
#include "qemu/thread.h"
#define TYPE_IOTHREAD "iothread"
typedef struct {
Object parent_obj;
QemuThread thread;
AioContext *ctx;
GMainContext *worker_context;
GMainLoop *main_loop;
GOnce once;
QemuMutex init_done_lock;
QemuCond init_done_cond; /* is thread initialization done? */
bool stopping; /* has iothread_stop() been called? */
bool running; /* should iothread_run() continue? */
int thread_id;
/* AioContext poll parameters */
int64_t poll_max_ns;
int64_t poll_grow;
int64_t poll_shrink;
} IOThread;
#define IOTHREAD(obj) \
OBJECT_CHECK(IOThread, obj, TYPE_IOTHREAD)
char *iothread_get_id(IOThread *iothread);
IOThread *iothread_by_id(const char *id);
AioContext *iothread_get_aio_context(IOThread *iothread);
GMainContext *iothread_get_g_main_context(IOThread *iothread);
/*
* Helpers used to allocate iothreads for internal use. These
* iothreads will not be seen by monitor clients when query using
* "query-iothreads".
*/
IOThread *iothread_create(const char *id, Error **errp);
void iothread_stop(IOThread *iothread);
void iothread_destroy(IOThread *iothread);
#endif /* IOTHREAD_H */