Re: [PATCH v3 4/9] vhost: Add kthread support in function vhost_worker_create

[Cindy Lu <lulu@redhat.com>]

On Tue, Nov 5, 2024 at 5:36 PM Jason Wang <jasowang@redhat.com> wrote:
>
> On Tue, Nov 5, 2024 at 3:27 PM Cindy Lu <lulu@redhat.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@redhat.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.
>
will fix this
> > +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.
>
sure, will fix this
> > +       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?
>
sure, will change this part
thanks
cindy
> >
> >  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
>