linux-kernel - Re: [PATCH v2 3/7] vhost: Add kthread support in function vhost_workers

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Message-ID: <4z4lgkittsui6xv26h4gwo4o4xuut4sbcih6p7jxajwignftyq@catixvwskk5m>
Date: Mon, 7 Oct 2024 15:32:48 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Cindy Lu <lulu@...hat.com>
Cc: jasowang@...hat.com, mst@...hat.com, michael.christie@...cle.com, 
	linux-kernel@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v2 3/7] vhost: Add kthread support in function
 vhost_workers_free()

On Fri, Oct 04, 2024 at 09:58:17AM GMT, Cindy Lu wrote:
>Added back the previously removed function vhost_workers_free() and
>renamed it to vhost_workers_free_khtread(). The new vhost_workers_free()
>will select the different mode based on the value of the parameter.
>
>The old function vhost_workers_free was change to support task in
>commit 6e890c5d5021 ("vhost: use vhost_tasks for worker threads")
>also changed in
>commit a284f09effea ("vhost: Fix crash during early vhost_transport_send_pkt calls")
>change to xarray in
>commit 1cdaafa1b8b4 ("vhost: replace single worker pointer with xarray")
>
>Signed-off-by: Cindy Lu <lulu@...hat.com>
>---
> drivers/vhost/vhost.c | 52 ++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 47 insertions(+), 5 deletions(-)
>
>diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>index ad359d4b725f..fed6671c1ffb 100644
>--- a/drivers/vhost/vhost.c
>+++ b/drivers/vhost/vhost.c
>@@ -648,8 +648,21 @@ static void vhost_detach_mm(struct vhost_dev *dev)
> 	dev->mm = NULL;
> }
>
>-static void vhost_worker_destroy(struct vhost_dev *dev,
>-				 struct vhost_worker *worker)
>+static void vhost_worker_destroy_kthread(struct vhost_dev *dev,
>+					 struct vhost_worker *worker)
>+{
>+	if (!worker)
>+		return;
>+
>+	WARN_ON(!llist_empty(&worker->work_list));
>+
>+	xa_erase(&dev->worker_xa, worker->id);
>+	kthread_stop(worker->task);
>+	kfree(worker);
>+}
>+
>+static void vhost_worker_destroy_task(struct vhost_dev *dev,
>+				      struct vhost_worker *worker)
> {
> 	if (!worker)
> 		return;
>@@ -660,7 +673,7 @@ static void vhost_worker_destroy(struct vhost_dev *dev,
> 	kfree(worker);
> }
>
>-static void vhost_workers_free(struct vhost_dev *dev)
>+static void vhost_workers_free_task(struct vhost_dev *dev)
> {
> 	struct vhost_worker *worker;
> 	unsigned long i;
>@@ -675,10 +688,36 @@ static void vhost_workers_free(struct vhost_dev *dev)
> 	 * created but couldn't clean up (it forgot or crashed).
> 	 */
> 	xa_for_each(&dev->worker_xa, i, worker)
>-		vhost_worker_destroy(dev, worker);
>+		vhost_worker_destroy_task(dev, worker);
> 	xa_destroy(&dev->worker_xa);
> }
>
>+static void vhost_workers_free_kthread(struct vhost_dev *dev)
>+{
>+	struct vhost_worker *worker;
>+	unsigned long i;
>+
>+	if (!dev->use_worker)
>+		return;
>+
>+	for (i = 0; i < dev->nvqs; i++)
>+		rcu_assign_pointer(dev->vqs[i]->worker, NULL);
>+	/*
>+	 * Free the default worker we created and cleanup workers userspace
>+	 * created but couldn't clean up (it forgot or crashed).
>+	 */
>+	xa_for_each(&dev->worker_xa, i, worker)
>+		vhost_worker_destroy_kthread(dev, worker);
>+	xa_destroy(&dev->worker_xa);
>+}
>+
>+static void vhost_workers_free(struct vhost_dev *dev)
>+{
>+	if (enforce_inherit_owner)
>+		vhost_workers_free_task(dev);
>+	else
>+		vhost_workers_free_kthread(dev);
>+}

nit: new line here

> static struct vhost_worker *vhost_worker_create(struct vhost_dev *dev)
> {
> 	struct vhost_worker *worker;
>@@ -846,7 +885,10 @@ static int vhost_free_worker(struct vhost_dev *dev,
> 	__vhost_worker_flush(worker);
> 	mutex_unlock(&worker->mutex);
>
>-	vhost_worker_destroy(dev, worker);
>+	if (enforce_inherit_owner)
>+		vhost_worker_destroy_task(dev, worker);
>+	else
>+		vhost_worker_destroy_kthread(dev, worker);
> 	return 0;
> }
>
>-- 
>2.45.0
>
>