Re: [PATCH v2 7/8] vdpa_sim: replace the spinlock with a mutex to protect the state

Jason Wang
2023-03-14T05:30:31Z

On Thu, Mar 2, 2023 at 7:35 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
>
> The spinlock we use to protect the state of the simulator is sometimes
> held for a long time (for example, when devices handle requests).
>
> This also prevents us from calling functions that might sleep (such as
> kthread_flush_work() in the next patch), and thus having to release
> and retake the lock.
>
> For these reasons, let's replace the spinlock with a mutex that gives
> us more flexibility.
>
> Suggested-by: Jason Wang <jasowang@redhat.com>
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>

Acked-by: Jason Wang <jasowang@redhat.com>

Thanks

> ---
> drivers/vdpa/vdpa_sim/vdpa_sim.h | 4 ++--
> drivers/vdpa/vdpa_sim/vdpa_sim.c | 34 ++++++++++++++--------------
> drivers/vdpa/vdpa_sim/vdpa_sim_blk.c | 4 ++--
> drivers/vdpa/vdpa_sim/vdpa_sim_net.c | 4 ++--
> 4 files changed, 23 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.h b/drivers/vdpa/vdpa_sim/vdpa_sim.h
> index ce83f9130a5d..4774292fba8c 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.h
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.h
> @@ -60,8 +60,8 @@ struct vdpasim {
> struct kthread_worker *worker;
> struct kthread_work work;
> struct vdpasim_dev_attr dev_attr;
> - /* spinlock to synchronize virtqueue state */
> - spinlock_t lock;
> + /* mutex to synchronize virtqueue state */
> + struct mutex mutex;
> /* virtio config according to device type */
> void *config;
> struct vhost_iotlb *iommu;
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> index 6feb29726c2a..a28103a67ae7 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> @@ -166,7 +166,7 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
> if (IS_ERR(vdpasim->worker))
> goto err_iommu;
>
> - spin_lock_init(&vdpasim->lock);
> + mutex_init(&vdpasim->mutex);
> spin_lock_init(&vdpasim->iommu_lock);
>
> dev = &vdpasim->vdpa.dev;
> @@ -275,13 +275,13 @@ static void vdpasim_set_vq_ready(struct vdpa_device *vdpa, u16 idx, bool ready)
> struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
> bool old_ready;
>
> - spin_lock(&vdpasim->lock);
> + mutex_lock(&vdpasim->mutex);
> old_ready = vq->ready;
> vq->ready = ready;
> if (vq->ready && !old_ready) {
> vdpasim_queue_ready(vdpasim, idx);
> }
> - spin_unlock(&vdpasim->lock);
> + mutex_unlock(&vdpasim->mutex);
> }
>
> static bool vdpasim_get_vq_ready(struct vdpa_device *vdpa, u16 idx)
> @@ -299,9 +299,9 @@ static int vdpasim_set_vq_state(struct vdpa_device *vdpa, u16 idx,
> struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
> struct vringh *vrh = &vq->vring;
>
> - spin_lock(&vdpasim->lock);
> + mutex_lock(&vdpasim->mutex);
> vrh->last_avail_idx = state->split.avail_index;
> - spin_unlock(&vdpasim->lock);
> + mutex_unlock(&vdpasim->mutex);
>
> return 0;
> }
> @@ -398,9 +398,9 @@ static u8 vdpasim_get_status(struct vdpa_device *vdpa)
> struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
> u8 status;
>
> - spin_lock(&vdpasim->lock);
> + mutex_lock(&vdpasim->mutex);
> status = vdpasim->status;
> - spin_unlock(&vdpasim->lock);
> + mutex_unlock(&vdpasim->mutex);
>
> return status;
> }
> @@ -409,19 +409,19 @@ static void vdpasim_set_status(struct vdpa_device *vdpa, u8 status)
> {
> struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
>
> - spin_lock(&vdpasim->lock);
> + mutex_lock(&vdpasim->mutex);
> vdpasim->status = status;
> - spin_unlock(&vdpasim->lock);
> + mutex_unlock(&vdpasim->mutex);
> }
>
> static int vdpasim_reset(struct vdpa_device *vdpa)
> {
> struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
>
> - spin_lock(&vdpasim->lock);
> + mutex_lock(&vdpasim->mutex);
> vdpasim->status = 0;
> vdpasim_do_reset(vdpasim);
> - spin_unlock(&vdpasim->lock);
> + mutex_unlock(&vdpasim->mutex);
>
> return 0;
> }
> @@ -430,9 +430,9 @@ static int vdpasim_suspend(struct vdpa_device *vdpa)
> {
> struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
>
> - spin_lock(&vdpasim->lock);
> + mutex_lock(&vdpasim->mutex);
> vdpasim->running = false;
> - spin_unlock(&vdpasim->lock);
> + mutex_unlock(&vdpasim->mutex);
>
> return 0;
> }
> @@ -442,7 +442,7 @@ static int vdpasim_resume(struct vdpa_device *vdpa)
> struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
> int i;
>
> - spin_lock(&vdpasim->lock);
> + mutex_lock(&vdpasim->mutex);
> vdpasim->running = true;
>
> if (vdpasim->pending_kick) {
> @@ -453,7 +453,7 @@ static int vdpasim_resume(struct vdpa_device *vdpa)
> vdpasim->pending_kick = false;
> }
>
> - spin_unlock(&vdpasim->lock);
> + mutex_unlock(&vdpasim->mutex);
>
> return 0;
> }
> @@ -525,14 +525,14 @@ static int vdpasim_set_group_asid(struct vdpa_device *vdpa, unsigned int group,
>
> iommu = &vdpasim->iommu[asid];
>
> - spin_lock(&vdpasim->lock);
> + mutex_lock(&vdpasim->mutex);
>
> for (i = 0; i < vdpasim->dev_attr.nvqs; i++)
> if (vdpasim_get_vq_group(vdpa, i) == group)
> vringh_set_iotlb(&vdpasim->vqs[i].vring, iommu,
> &vdpasim->iommu_lock);
>
> - spin_unlock(&vdpasim->lock);
> + mutex_unlock(&vdpasim->mutex);
>
> return 0;
> }
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> index eb4897c8541e..568119e1553f 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> @@ -290,7 +290,7 @@ static void vdpasim_blk_work(struct vdpasim *vdpasim)
> bool reschedule = false;
> int i;
>
> - spin_lock(&vdpasim->lock);
> + mutex_lock(&vdpasim->mutex);
>
> if (!(vdpasim->status & VIRTIO_CONFIG_S_DRIVER_OK))
> goto out;
> @@ -321,7 +321,7 @@ static void vdpasim_blk_work(struct vdpasim *vdpasim)
> }
> }
> out:
> - spin_unlock(&vdpasim->lock);
> + mutex_unlock(&vdpasim->mutex);
>
> if (reschedule)
> vdpasim_schedule_work(vdpasim);
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_net.c b/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
> index e61a9ecbfafe..7ab434592bfe 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim_net.c
> @@ -201,7 +201,7 @@ static void vdpasim_net_work(struct vdpasim *vdpasim)
> u64 rx_drops = 0, rx_overruns = 0, rx_errors = 0, tx_errors = 0;
> int err;
>
> - spin_lock(&vdpasim->lock);
> + mutex_lock(&vdpasim->mutex);
>
> if (!vdpasim->running)
> goto out;
> @@ -264,7 +264,7 @@ static void vdpasim_net_work(struct vdpasim *vdpasim)
> }
>
> out:
> - spin_unlock(&vdpasim->lock);
> + mutex_unlock(&vdpasim->mutex);
>
> u64_stats_update_begin(&net->tx_stats.syncp);
> net->tx_stats.pkts += tx_pkts;
> --
> 2.39.2
>