diff mbox series

[v6,16/20] virtio: make it possible to detach host notifier from any thread

Message ID 20230516190238.8401-17-stefanha@redhat.com
State New
Headers show
Series block: remove aio_disable_external() API | expand

Commit Message

Stefan Hajnoczi May 16, 2023, 7:02 p.m. UTC 
virtio_queue_aio_detach_host_notifier() does two things:
1. It removes the fd handler from the event loop.
2. It processes the virtqueue one last time.

The first step can be peformed by any thread and without taking the
AioContext lock.

The second step may need the AioContext lock (depending on the device
implementation) and runs in the thread where request processing takes
place. virtio-blk and virtio-scsi therefore call
virtio_queue_aio_detach_host_notifier() from a BH that is scheduled in
AioContext.

The next patch will introduce a .drained_begin() function that needs to
call virtio_queue_aio_detach_host_notifier(). .drained_begin() functions
cannot call aio_poll() to wait synchronously for the BH. It is possible
for a .drained_poll() callback to asynchronously wait for the BH, but
that is more complex than necessary here.

Move the virtqueue processing out to the callers of
virtio_queue_aio_detach_host_notifier() so that the function can be
called from any thread. This is in preparation for the next patch.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/block/dataplane/virtio-blk.c |  7 +++++++
 hw/scsi/virtio-scsi-dataplane.c | 14 ++++++++++++++
 hw/virtio/virtio.c              |  3 ---
 3 files changed, 21 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index af1c24c40c..4f5c7cd55f 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -287,8 +287,15 @@  static void virtio_blk_data_plane_stop_bh(void *opaque)
 
     for (i = 0; i < s->conf->num_queues; i++) {
         VirtQueue *vq = virtio_get_queue(s->vdev, i);
+        EventNotifier *host_notifier = virtio_queue_get_host_notifier(vq);
 
         virtio_queue_aio_detach_host_notifier(vq, s->ctx);
+
+        /*
+         * Test and clear notifier after disabling event, in case poll callback
+         * didn't have time to run.
+         */
+        virtio_queue_host_notifier_read(host_notifier);
     }
 }
 
diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c
index f3214e1c57..b3a1ed21f7 100644
--- a/hw/scsi/virtio-scsi-dataplane.c
+++ b/hw/scsi/virtio-scsi-dataplane.c
@@ -71,12 +71,26 @@  static void virtio_scsi_dataplane_stop_bh(void *opaque)
 {
     VirtIOSCSI *s = opaque;
     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
+    EventNotifier *host_notifier;
     int i;
 
     virtio_queue_aio_detach_host_notifier(vs->ctrl_vq, s->ctx);
+    host_notifier = virtio_queue_get_host_notifier(vs->ctrl_vq);
+
+    /*
+     * Test and clear notifier after disabling event, in case poll callback
+     * didn't have time to run.
+     */
+    virtio_queue_host_notifier_read(host_notifier);
+
     virtio_queue_aio_detach_host_notifier(vs->event_vq, s->ctx);
+    host_notifier = virtio_queue_get_host_notifier(vs->event_vq);
+    virtio_queue_host_notifier_read(host_notifier);
+
     for (i = 0; i < vs->conf.num_queues; i++) {
         virtio_queue_aio_detach_host_notifier(vs->cmd_vqs[i], s->ctx);
+        host_notifier = virtio_queue_get_host_notifier(vs->cmd_vqs[i]);
+        virtio_queue_host_notifier_read(host_notifier);
     }
 }
 
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 272d930721..cb09cb6464 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -3516,9 +3516,6 @@  void virtio_queue_aio_attach_host_notifier_no_poll(VirtQueue *vq, AioContext *ct
 void virtio_queue_aio_detach_host_notifier(VirtQueue *vq, AioContext *ctx)
 {
     aio_set_event_notifier(ctx, &vq->host_notifier, true, NULL, NULL, NULL);
-    /* Test and clear notifier before after disabling event,
-     * in case poll callback didn't have time to run. */
-    virtio_queue_host_notifier_read(&vq->host_notifier);
 }
 
 void virtio_queue_host_notifier_read(EventNotifier *n)