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Message-ID: <CACLfguVT_5Njx3Sq18st3K=+dzE2Rv7HUa+oX_XV+WXrzOjD_Q@mail.gmail.com>
Date: Wed, 8 Jan 2025 10:52:46 +0800
From: Cindy Lu <lulu@...hat.com>
To: Jason Wang <jasowang@...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 Thu, Jan 2, 2025 at 11:33 AM Jason Wang <jasowang@...hat.com> wrote:
>
> 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.
>
sure will change this
> >
> > 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.
>
will change this
> > + } 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
>
sure will do
Thanks
cindy
> > };
> >
> > /* Poll a file (eventfd or socket) */
> > --
> > 2.45.0
> >
>
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