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

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Message-ID: <CACGkMEur=CoU1GgxNdweu-SfuutSN-a+LaHLkdtoWYJMnE+LOg@mail.gmail.com>
Date: Tue, 21 May 2024 10:32:32 +0800
From: Jason Wang <jasowang@...hat.com>
To: Steve Sistare <steven.sistare@...cle.com>
Cc: virtualization@...ts.linux-foundation.org, linux-kernel@...r.kernel.org, 
	"Michael S. Tsirkin" <mst@...hat.com>, Si-Wei Liu <si-wei.liu@...cle.com>, 
	Eugenio Perez Martin <eperezma@...hat.com>, Xie Yongji <xieyongji@...edance.com>, 
	Stefano Garzarella <sgarzare@...hat.com>
Subject: Re: [PATCH V3 3/3] vdpa_sim: flush workers on suspend

On Mon, May 20, 2024 at 11:21 PM Steve Sistare
<steven.sistare@...cle.com> 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@...cle.com>
> ---
>  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?

Thanks

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