Re: [PATCH v2 6/8] vdpa_sim: use kthread worker

[Stefano Garzarella]

On Thu, Mar 02, 2023 at 04:30:04PM +0100, Simon Horman wrote:
> On Thu, Mar 02, 2023 at 12:34:19PM +0100, Stefano Garzarella wrote:
> > Let's use our own kthread to run device jobs.
> > This allows us more flexibility, especially we can attach the kthread
> > to the user address space when vDPA uses user's VA.
> >
> > Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
> > ---
> >  drivers/vdpa/vdpa_sim/vdpa_sim.h |  3 ++-
> >  drivers/vdpa/vdpa_sim/vdpa_sim.c | 17 ++++++++++++-----
> >  2 files changed, 14 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.h b/drivers/vdpa/vdpa_sim/vdpa_sim.h
> > index acee20faaf6a..ce83f9130a5d 100644
> > --- a/drivers/vdpa/vdpa_sim/vdpa_sim.h
> > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.h
> > @@ -57,7 +57,8 @@ struct vdpasim_dev_attr {
> >  struct vdpasim {
> >  	struct vdpa_device vdpa;
> >  	struct vdpasim_virtqueue *vqs;
> > -	struct work_struct work;
> > +	struct kthread_worker *worker;
> > +	struct kthread_work work;
> >  	struct vdpasim_dev_attr dev_attr;
> >  	/* spinlock to synchronize virtqueue state */
> >  	spinlock_t lock;
> > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > index a6ee830efc38..6feb29726c2a 100644
> > --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > @@ -11,8 +11,8 @@
> >  #include <linux/module.h>
> >  #include <linux/device.h>
> >  #include <linux/kernel.h>
> > +#include <linux/kthread.h>
> >  #include <linux/slab.h>
> > -#include <linux/sched.h>
> >  #include <linux/dma-map-ops.h>
> >  #include <linux/vringh.h>
> >  #include <linux/vdpa.h>
> > @@ -116,7 +116,7 @@ static void vdpasim_do_reset(struct vdpasim *vdpasim)
> >  static const struct vdpa_config_ops vdpasim_config_ops;
> >  static const struct vdpa_config_ops vdpasim_batch_config_ops;
> >
> > -static void vdpasim_work_fn(struct work_struct *work)
> > +static void vdpasim_work_fn(struct kthread_work *work)
> >  {
> >  	struct vdpasim *vdpasim = container_of(work, struct vdpasim, work);
> >
> > @@ -159,7 +159,13 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
> >
> >  	vdpasim = vdpa_to_sim(vdpa);
> >  	vdpasim->dev_attr = *dev_attr;
> > -	INIT_WORK(&vdpasim->work, vdpasim_work_fn);
> > +
> > +	kthread_init_work(&vdpasim->work, vdpasim_work_fn);
> > +	vdpasim->worker = kthread_create_worker(0, "vDPA sim worker: %s",
> > +						dev_attr->name);
> > +	if (IS_ERR(vdpasim->worker))
> > +		goto err_iommu;
>
> Branching to err_iommu will result in a call to put_device(dev)...

Good catch!

> > +
> >  	spin_lock_init(&vdpasim->lock);
> >  	spin_lock_init(&vdpasim->iommu_lock);
>
> ... but dev is not initialised until the line following this hunk,
> which is:
>
> 	dev = &vdpasim->vdpa.dev;
>
> In order to avoid leaking dev I _think_ the correct approach
> is to move the initialisation of dev above the branch to
> err_iommu, perhaps above the call to kthread_init_work()
> is a good place.

Yep, I agree. I'll fix in v3.

Thanks,
Stefano

> This does move the assignment outside the locks above.
> But I _think_ that is ok.
>
> > @@ -212,7 +218,7 @@ EXPORT_SYMBOL_GPL(vdpasim_create);
> >
> >  void vdpasim_schedule_work(struct vdpasim *vdpasim)
> >  {
> > -	schedule_work(&vdpasim->work);
> > +	kthread_queue_work(vdpasim->worker, &vdpasim->work);
> >  }
> >  EXPORT_SYMBOL_GPL(vdpasim_schedule_work);
> >
> > @@ -612,7 +618,8 @@ static void vdpasim_free(struct vdpa_device *vdpa)
> >  	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
> >  	int i;
> >
> > -	cancel_work_sync(&vdpasim->work);
> > +	kthread_cancel_work_sync(&vdpasim->work);
> > +	kthread_destroy_worker(vdpasim->worker);
> >
> >  	for (i = 0; i < vdpasim->dev_attr.nvqs; i++) {
> >  		vringh_kiov_cleanup(&vdpasim->vqs[i].out_iov);
> > --
> > 2.39.2