Message-ID: <CACGkMEvwirx3C7QL_xYB_niYBYfugCR9OMWqwcPfAPX=E1Qm=Q@mail.gmail.com>
Date: Tue, 5 Nov 2024 17:36:10 +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 v3 4/9] vhost: Add kthread support in function vhost_worker_create

On Tue, Nov 5, 2024 at 3:27 PM Cindy Lu <lulu@...hat.com> wrote:
>
> Restored the previous functions kthread_wakeup and kthread_stop.
> Also add a new structure, vhost_task_fn. The function vhost_worker_create
> Will initializes this structure based on the value of inherit_owner.
>
> Signed-off-by: Cindy Lu <lulu@...hat.com>
> ---
>  drivers/vhost/vhost.c | 71 ++++++++++++++++++++++++++++++++++++-------
>  drivers/vhost/vhost.h |  6 ++++
>  2 files changed, 66 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index e40cef3a1fa5..603b146fccc1 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -741,43 +741,92 @@ static void vhost_workers_free(struct vhost_dev *dev)
>         xa_destroy(&dev->worker_xa);
>  }
>
> +static int vhost_task_wakeup_fn(void *vtsk)
> +{
> +       vhost_task_wake((struct vhost_task *)vtsk);
> +       return 0;
> +}

Let's have a newline between two functions.

> +static int vhost_kthread_wakeup_fn(void *p)
> +{
> +       return wake_up_process((struct task_struct *)p);
> +}
> +static int vhost_task_stop_fn(void *vtsk)
> +{
> +       vhost_task_stop((struct vhost_task *)vtsk);
> +       return 0;
> +}
> +static int vhost_kthread_stop_fn(void *k)
> +{
> +       return kthread_stop((struct task_struct *)k);
> +}
> +
>  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;
>
> +       worker->fn = kzalloc(sizeof(struct vhost_task_fn), GFP_KERNEL_ACCOUNT);
> +       if (!worker->fn) {
> +               kfree(worker);
> +               return NULL;
> +       }
> +
>         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;
>
> -       vhost_task_start(vtsk);
> +       if (dev->inherit_owner) {
> +               /* Create and start a vhost task */
> +               vtsk = vhost_task_create(vhost_run_work_list,
> +                                        vhost_worker_killed, worker, name);
> +               if (!vtsk)
> +                       goto free_worker;
> +
> +               worker->vtsk = vtsk;
> +               worker->fn->wakeup = vhost_task_wakeup_fn;
> +               worker->fn->stop = vhost_task_stop_fn;
> +
> +               vhost_task_start(vtsk);
> +       } else {
> +               /* Create and start a kernel thread */
> +               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->task = task;
> +               worker->fn->wakeup = vhost_kthread_wakeup_fn;
> +               worker->fn->stop = vhost_kthread_stop_fn;
> +
> +               wake_up_process(task);
> +               /* Attach to the vhost cgroup */
> +               ret = vhost_attach_cgroups(dev);
> +               if (ret)
> +                       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;
> -
>         return worker;
> -
>  stop_worker:
> -       vhost_task_stop(vtsk);
> +       worker->fn->stop(dev->inherit_owner ? (void *)vtsk : (void *)task);
>  free_worker:
> +       kfree(worker->fn);
>         kfree(worker);
>         return NULL;
>  }
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index c650c4506c70..ebababa4e340 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -25,8 +25,13 @@ struct vhost_work {
>         vhost_work_fn_t         fn;
>         unsigned long           flags;
>  };
> +struct vhost_task_fn {
> +       int (*wakeup)(void *task);

Let's have comments to explain the semantics of each operation.

> +       int (*stop)(void *task);
> +};

I think the goal is to reduce if/else, so while at this, let's
introduce more ops. For example the create_worker one?

>
>  struct vhost_worker {
> +       struct task_struct      *task;
>         struct vhost_task       *vtsk;
>         struct vhost_dev        *dev;
>         /* Used to serialize device wide flushing with worker swapping. */
> @@ -36,6 +41,7 @@ struct vhost_worker {
>         u32                     id;
>         int                     attachment_cnt;
>         bool                    killed;
> +       struct vhost_task_fn *fn;
>  };
>
>  /* Poll a file (eventfd or socket) */
> --
> 2.45.0
>

Thanks

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