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Tue, 15 Sep 2026 02:43:06 -0700 (PDT) From: physicalmtea@gmail.com To: mst@redhat.com Cc: jasowangio@gmail.com, michael.christie@oracle.com, pbonzini@redhat.com, stefanha@redhat.com, eperezma@redhat.com, nab@linux-iscsi.org, asias@redhat.com, virtualization@lists.linux.dev, kvm@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 2/2] vhost-scsi: do not relock event vq mutex on send_evt fallback Date: Tue, 15 Sep 2026 17:42:44 +0800 Message-Id: <20260915094244.7900-3-physicalmtea@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260915094244.7900-1-physicalmtea@gmail.com> References: <20260915094244.7900-1-physicalmtea@gmail.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Jia Jia 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: b1b2ce58ed23 ("vhost-scsi: Handle vhost_vq_work_queue failures for events") Signed-off-by: Jia Jia Reviewed-by: Mike Christie --- drivers/vhost/scsi.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c index 37f681aab..9cd181cb1 100644 --- a/drivers/vhost/scsi.c +++ b/drivers/vhost/scsi.c @@ -630,19 +630,26 @@ 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); } @@ -1829,7 +1836,7 @@ 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) -- 2.34.1