From f5191917a704d78617db4af8c9da53dc6f2004b7 Mon Sep 17 00:00:00 2001 From: Mike Christie Date: Fri, 15 Mar 2024 19:47:04 -0500 Subject: [PATCH] vhost: Use virtqueue mutex for swapping worker BugLink: https://bugs.launchpad.net/bugs/2077600 [ Upstream commit 34cf9ba5f00a222dddd9fc71de7c68fdaac7fb97 ] __vhost_vq_attach_worker uses the vhost_dev mutex to serialize the swapping of a virtqueue's worker. This was done for simplicity because we are already holding that mutex. In the next patches where the worker can be killed while in use, we need finer grained locking because some drivers will hold the vhost_dev mutex while flushing. However in the SIGKILL handler in the next patches, we will need to be able to swap workers (set current one to NULL), kill queued works and stop new flushes while flushes are in progress. To prepare us, this has us use the virtqueue mutex for swapping workers instead of the vhost_dev one. Signed-off-by: Mike Christie Message-Id: <20240316004707.45557-7-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin Signed-off-by: Sasha Levin Signed-off-by: Portia Stephens Signed-off-by: Roxana Nicolescu --- drivers/vhost/vhost.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 32686c79c41d..9d1db2019e30 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -664,16 +664,22 @@ static void __vhost_vq_attach_worker(struct vhost_virtqueue *vq, { struct vhost_worker *old_worker; - old_worker = rcu_dereference_check(vq->worker, - lockdep_is_held(&vq->dev->mutex)); - mutex_lock(&worker->mutex); - worker->attachment_cnt++; - mutex_unlock(&worker->mutex); - rcu_assign_pointer(vq->worker, worker); + mutex_lock(&vq->mutex); - if (!old_worker) + old_worker = rcu_dereference_check(vq->worker, + lockdep_is_held(&vq->mutex)); + rcu_assign_pointer(vq->worker, worker); + worker->attachment_cnt++; + + if (!old_worker) { + mutex_unlock(&vq->mutex); + mutex_unlock(&worker->mutex); return; + } + mutex_unlock(&vq->mutex); + mutex_unlock(&worker->mutex); + /* * Take the worker mutex to make sure we see the work queued from * device wide flushes which doesn't use RCU for execution.