Re: [PATCH V3 3/3] vdpa_sim: flush workers on suspend

[Steven Sistare <steven.sistare@xxxxxxxxxx>]

On 5/20/2024 10:32 PM, Jason Wang wrote:
> On Mon, May 20, 2024 at 11:21 PM Steve Sistare
> <steven.sistare@xxxxxxxxxx> wrote:
> > Flush to guarantee no workers are running when suspend returns.
> > Add a lock to enforce ordering between clearing running, flushing,
> > and posting new work in vdpasim_kick_vq.  It must be a spin lock
> > because vdpasim_kick_vq may be reached va eventfd_write.
> >
> > Signed-off-by: Steve Sistare <steven.sistare@xxxxxxxxxx>
> > ---
> >   drivers/vdpa/vdpa_sim/vdpa_sim.c | 16 ++++++++++++++--
> >   drivers/vdpa/vdpa_sim/vdpa_sim.h |  1 +
> >   2 files changed, 15 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > index 8ffea8430f95..67ed49d95bf0 100644
> > --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > @@ -322,7 +322,7 @@ static u16 vdpasim_get_vq_size(struct vdpa_device *vdpa, u16 idx)
> >                  return VDPASIM_QUEUE_MAX;
> >   }
> >
> > -static void vdpasim_kick_vq(struct vdpa_device *vdpa, u16 idx)
> > +static void vdpasim_do_kick_vq(struct vdpa_device *vdpa, u16 idx)
> >   {
> >          struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
> >          struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
> > @@ -337,6 +337,15 @@ static void vdpasim_kick_vq(struct vdpa_device *vdpa, u16 idx)
> >                  vdpasim_schedule_work(vdpasim);
> >   }
> >
> > +static void vdpasim_kick_vq(struct vdpa_device *vdpa, u16 idx)
> > +{
> > +       struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
> > +
> > +       spin_lock(&vdpasim->kick_lock);
> > +       vdpasim_do_kick_vq(vdpa, idx);
> > +       spin_unlock(&vdpasim->kick_lock);
> > +}
> > +
> >   static void vdpasim_set_vq_cb(struct vdpa_device *vdpa, u16 idx,
> >                                struct vdpa_callback *cb)
> >   {
> > @@ -520,8 +529,11 @@ static int vdpasim_suspend(struct vdpa_device *vdpa)
> >          struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
> >
> >          mutex_lock(&vdpasim->mutex);
> > +       spin_lock(&vdpasim->kick_lock);
> >          vdpasim->running = false;
> > +       spin_unlock(&vdpasim->kick_lock);
> >          mutex_unlock(&vdpasim->mutex);
> > +       kthread_flush_work(&vdpasim->work);
> >
> >          return 0;
> >   }
> > @@ -537,7 +549,7 @@ static int vdpasim_resume(struct vdpa_device *vdpa)
> >          if (vdpasim->pending_kick) {
> >                  /* Process pending descriptors */
> >                  for (i = 0; i < vdpasim->dev_attr.nvqs; ++i)
> > -                       vdpasim_kick_vq(vdpa, i);
> > +                       vdpasim_do_kick_vq(vdpa, i);
> >
> >                  vdpasim->pending_kick = false;
> >          }
> > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.h b/drivers/vdpa/vdpa_sim/vdpa_sim.h
> > index bb137e479763..5eb6ca9c5ec5 100644
> > --- a/drivers/vdpa/vdpa_sim/vdpa_sim.h
> > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.h
> > @@ -75,6 +75,7 @@ struct vdpasim {
> >          bool pending_kick;
> >          /* spinlock to synchronize iommu table */
> >          spinlock_t iommu_lock;
> > +       spinlock_t kick_lock;
>
> It looks to me this is not initialized?

Yup, I lost that line while fiddling with different locking schemes.
Thanks, will fix in V4.

@@ -236,6 +236,7 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr 
*dev_attr,

        mutex_init(&vdpasim->mutex);
        spin_lock_init(&vdpasim->iommu_lock);
+       spin_lock_init(&vdpasim->kick_lock);

With that fix, does this patch earn your RB?

- Steve

> >   };
> >
> >   struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *attr,
> > --
> > 2.39.3