linux-kernel - Re: [PATCH v8 2/8] vhost: Reintroduce vhost

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Message-ID: <ylnfh4mwifvrnmlwpg6g4mjtfzc7z5qvn5hnnvxz6cepbkobcg@hsv3z2yp5w3f>
Date: Tue, 1 Apr 2025 15:38:02 +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, 
	netdev@...r.kernel.org
Subject: Re: [PATCH v8 2/8] vhost: Reintroduce vhost_worker to support kthread

On Fri, Mar 28, 2025 at 06:02:46PM +0800, Cindy Lu wrote:
>Add the previously removed function vhost_worker() back
>to support the kthread and rename it to vhost_run_work_kthread_list.
>
>The old function vhost_worker was change to support task in

nit: s/change/changed

>commit 6e890c5d5021 ("vhost: use vhost_tasks for worker threads")
>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 | 38 ++++++++++++++++++++++++++++++++++++++
> 1 file changed, 38 insertions(+)

I tried to build commit by commit (mainly to check bisection), and I
discovered that nowdays unused functions produce an error (yes, we can 
mute it for example by setting CONFIG_WERROR to N), but I wanted to 
point it out:

../drivers/vhost/vhost.c:391:12: error: ‘vhost_run_work_kthread_list’ defined but not used [-Werror=unused-function]
   391 | static int vhost_run_work_kthread_list(void *data)

So not sure if we need to squash this where we use it.

Same issue also for the next 2 patches.

Thanks,
Stefano

>
>diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>index 250dc43f1786..9500e85b42ce 100644
>--- a/drivers/vhost/vhost.c
>+++ b/drivers/vhost/vhost.c
>@@ -388,6 +388,44 @@ static void vhost_vq_reset(struct vhost_dev *dev,
> 	__vhost_vq_meta_reset(vq);
> }
>
>+static int vhost_run_work_kthread_list(void *data)
>+{
>+	struct vhost_worker *worker = data;
>+	struct vhost_work *work, *work_next;
>+	struct vhost_dev *dev = worker->dev;
>+	struct llist_node *node;
>+
>+	kthread_use_mm(dev->mm);
>+
>+	for (;;) {
>+		/* mb paired w/ kthread_stop */
>+		set_current_state(TASK_INTERRUPTIBLE);
>+
>+		if (kthread_should_stop()) {
>+			__set_current_state(TASK_RUNNING);
>+			break;
>+		}
>+		node = llist_del_all(&worker->work_list);
>+		if (!node)
>+			schedule();
>+
>+		node = llist_reverse_order(node);
>+		/* make sure flag is seen after deletion */
>+		smp_wmb();
>+		llist_for_each_entry_safe(work, work_next, node, node) {
>+			clear_bit(VHOST_WORK_QUEUED, &work->flags);
>+			__set_current_state(TASK_RUNNING);
>+			kcov_remote_start_common(worker->kcov_handle);
>+			work->fn(work);
>+			kcov_remote_stop();
>+			cond_resched();
>+		}
>+	}
>+	kthread_unuse_mm(dev->mm);
>+
>+	return 0;
>+}
>+
> static bool vhost_run_work_list(void *data)
> {
> 	struct vhost_worker *worker = data;
>-- 
>2.45.0
>