6.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Mike Christie <michael.christie@xxxxxxxxxx>
[ 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 <michael.christie@xxxxxxxxxx>
Message-Id: <20240316004707.45557-7-michael.christie@xxxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Stable-dep-of: db5247d9bf5c ("vhost_task: Handle SIGKILL by flushing work and exiting")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/vhost/vhost.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 8995730ce0bfc..113b6a42719b7 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);
+ mutex_lock(&vq->mutex);
+
+ old_worker = rcu_dereference_check(vq->worker,
+ lockdep_is_held(&vq->mutex));
rcu_assign_pointer(vq->worker, worker);
+ worker->attachment_cnt++;
- if (!old_worker)
+ 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.
--
2.43.0
