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Message-ID: <CACGkMEtq3yRB=7r54=rdPC1TPrz00ayEkt+L1n=dQTTTTD58FA@mail.gmail.com>
Date: Thu, 2 Jan 2025 11:33:00 +0800
From: Jason Wang <jasowang@...hat.com>
To: Cindy Lu <lulu@...hat.com>
Cc: mst@...hat.com, michael.christie@...cle.com, sgarzare@...hat.com,
linux-kernel@...r.kernel.org, virtualization@...ts.linux-foundation.org,
netdev@...r.kernel.org
Subject: Re: [PATCH v5 4/6] vhost: Add worker related functions to support kthread
On Mon, Dec 30, 2024 at 8:45 PM Cindy Lu <lulu@...hat.com> wrote:
>
> Restore the previously removed functions kthread_wakeup and
> kthread_stop, and add two new function pointers to wake up and stop
> the workers. The function vhost_worker_create will initialize these
> pointers based on the value of inherit_owner.
>
> The functions vhost_worker_queue() and vhost_worker_destroy() will
> use the function pointer in vhost_worker, which is initialized
> according to the inherit_owner value.
I'd suggest using "vhost: introduce worker ops to support multiple
thread models" as the title.
>
> Signed-off-by: Cindy Lu <lulu@...hat.com>
> ---
> drivers/vhost/vhost.c | 84 ++++++++++++++++++++++++++++++++++---------
> drivers/vhost/vhost.h | 3 ++
> 2 files changed, 71 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 812dfd218bc2..ff17c42e2d1a 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -243,7 +243,7 @@ static void vhost_worker_queue(struct vhost_worker *worker,
> * test_and_set_bit() implies a memory barrier.
> */
> llist_add(&work->node, &worker->work_list);
> - vhost_task_wake(worker->vtsk);
> + worker->worker_wakeup(worker);
> }
> }
>
> @@ -698,7 +698,7 @@ static void vhost_worker_destroy(struct vhost_dev *dev,
>
> WARN_ON(!llist_empty(&worker->work_list));
> xa_erase(&dev->worker_xa, worker->id);
> - vhost_task_stop(worker->vtsk);
> + worker->worker_stop(worker);
> kfree(worker);
> }
>
> @@ -721,14 +721,36 @@ static void vhost_workers_free(struct vhost_dev *dev)
> xa_destroy(&dev->worker_xa);
> }
>
> +static void vhost_task_wakeup_fn(struct vhost_worker *worker)
> +{
> + return vhost_task_wake(worker->vtsk);
> +}
> +
> +static void vhost_kthread_wakeup_fn(struct vhost_worker *worker)
> +{
> + wake_up_process(worker->kthread_task);
> +}
> +
> +static void vhost_task_stop_fn(struct vhost_worker *worker)
> +{
> + return vhost_task_stop(worker->vtsk);
> +}
> +
> +static void vhost_kthread_stop_fn(struct vhost_worker *worker)
> +{
> + kthread_stop(worker->kthread_task);
> +}
> +
> static struct vhost_worker *vhost_worker_create(struct vhost_dev *dev)
> {
> struct vhost_worker *worker;
> - struct vhost_task *vtsk;
> + struct vhost_task *vtsk = NULL;
> + struct task_struct *task = NULL;
> char name[TASK_COMM_LEN];
> int ret;
> u32 id;
>
> + /* Allocate resources for the worker */
> worker = kzalloc(sizeof(*worker), GFP_KERNEL_ACCOUNT);
> if (!worker)
> return NULL;
> @@ -736,27 +758,57 @@ static struct vhost_worker *vhost_worker_create(struct vhost_dev *dev)
> worker->dev = dev;
> snprintf(name, sizeof(name), "vhost-%d", current->pid);
>
> - vtsk = vhost_task_create(vhost_run_work_list, vhost_worker_killed,
> - worker, name);
> - if (!vtsk)
> - goto free_worker;
> -
> mutex_init(&worker->mutex);
> init_llist_head(&worker->work_list);
> worker->kcov_handle = kcov_common_handle();
> - worker->vtsk = vtsk;
> + /*
> + * If inherit_owner is true we use vhost_tasks to create
> + * the worker so all settings/limits like cgroups, NPROC,
> + * scheduler, etc are inherited from the owner.
> + * If false,we use kthreads and only attach to the same
> + * cgroups as the owner for compat with older kernels.
> + */
> + if (dev->inherit_owner) {
> + vtsk = vhost_task_create(vhost_run_work_list,
> + vhost_worker_killed, worker, name);
> + if (!vtsk)
> + goto free_worker;
> +
> + worker->vtsk = vtsk;
> + worker->worker_wakeup = vhost_task_wakeup_fn;
> + worker->worker_stop = vhost_task_stop_fn;
> +
> + vhost_task_start(vtsk);
> + ret = xa_alloc(&dev->worker_xa, &id, worker, xa_limit_32b,
> + GFP_KERNEL);
> + if (ret < 0)
> + goto stop_worker;
Let's simply have a new ops like worker_create to avoid the if/else here.
> + } else {
> + task = kthread_create(vhost_run_work_kthread_list, worker,
> + "vhost-%d", current->pid);
> + if (IS_ERR(task)) {
> + ret = PTR_ERR(task);
> + goto free_worker;
> + }
> + worker->kthread_task = task;
> + worker->worker_wakeup = vhost_kthread_wakeup_fn;
> + worker->worker_stop = vhost_kthread_stop_fn;
>
> - vhost_task_start(vtsk);
> + wake_up_process(task);
> + ret = xa_alloc(&dev->worker_xa, &id, worker, xa_limit_32b,
> + GFP_KERNEL);
> + if (ret < 0)
> + goto stop_worker;
>
> - ret = xa_alloc(&dev->worker_xa, &id, worker, xa_limit_32b, GFP_KERNEL);
> - if (ret < 0)
> - goto stop_worker;
> - worker->id = id;
> + ret = vhost_attach_task_to_cgroups(worker);
> + if (ret)
> + goto stop_worker;
> + }
>
> + worker->id = id;
> return worker;
> -
> stop_worker:
> - vhost_task_stop(vtsk);
> + worker->worker_stop(worker);
> free_worker:
> kfree(worker);
> return NULL;
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index c650c4506c70..63b1da08a2b0 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -27,6 +27,7 @@ struct vhost_work {
> };
>
> struct vhost_worker {
> + struct task_struct *kthread_task;
> struct vhost_task *vtsk;
> struct vhost_dev *dev;
> /* Used to serialize device wide flushing with worker swapping. */
> @@ -36,6 +37,8 @@ struct vhost_worker {
> u32 id;
> int attachment_cnt;
> bool killed;
> + void (*worker_wakeup)(struct vhost_worker *worker);
> + void (*worker_stop)(struct vhost_worker *worker);
Let's use a dedicated ops structure for this.
Thanks
> };
>
> /* Poll a file (eventfd or socket) */
> --
> 2.45.0
>
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