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vhost-scsi: do not relock event vq mutex on send_evt fallback

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vhost_scsi_send_evt() is called with the event virtqueue mutex held.
If the worker is gone, the fallback currently calls
vhost_scsi_complete_events(), which tries to acquire the same mutex again
and deadlocks the caller.

Split event completion into a helper for callers that already hold the
mutex and a locking wrapper for the event worker. Use the helper on the
fallback path.

Link: https://lore.kernel.org/all/20260905005352.1E5B01F00A3D@smtp.kernel.org/
Fixes: b1b2ce58ed ("vhost-scsi: Handle vhost_vq_work_queue failures for events")
Signed-off-by: Jia Jia <physicalmtea@gmail.com>
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20260915094244.7900-3-physicalmtea@gmail.com>
This commit is contained in:
Jia Jia 2026-09-15 17:42:44 +08:00 committed by Michael S. Tsirkin
parent a9a428115b
commit a016d03a9c
1 changed files with 11 additions and 4 deletions
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15
drivers/vhost/scsi.c
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@ -660,19 +660,26 @@ vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)
vhost_scsi_log_write(vq, vq_log, log_num);
}
static void vhost_scsi_complete_events(struct vhost_scsi *vs, bool drop)
/* Caller must hold the event virtqueue mutex. */
static void __vhost_scsi_complete_events(struct vhost_scsi *vs, bool drop)
{
struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
struct vhost_scsi_evt *evt, *t;
struct llist_node *llnode;
mutex_lock(&vq->mutex);
llnode = llist_reverse_order(llist_del_all(&vs->vs_event_list));
llist_for_each_entry_safe(evt, t, llnode, list) {
if (!drop)
vhost_scsi_do_evt_work(vs, evt);
vhost_scsi_free_evt(vs, evt);
}
}
static void vhost_scsi_complete_events(struct vhost_scsi *vs, bool drop)
{
struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
mutex_lock(&vq->mutex);
__vhost_scsi_complete_events(vs, drop);
mutex_unlock(&vq->mutex);
}
@ -1859,7 +1866,7 @@ vhost_scsi_send_evt(struct vhost_scsi *vs, struct vhost_virtqueue *vq,
llist_add(&evt->list, &vs->vs_event_list);
if (!vhost_vq_work_queue(vq, &vs->vs_event_work))
vhost_scsi_complete_events(vs, true);
__vhost_scsi_complete_events(vs, true);
}
static void vhost_scsi_evt_handle_kick(struct vhost_work *work)