[PATCH 1/1] drm/lima: implement the file flush callback

[Qiang Yu]

On Tue, Apr 8, 2025 at 11:48 PM Erico Nunes <nunes.erico at gmail.com> wrote:
>
> With this callback implemented, a terminating application will wait for
> the sched entity to be flushed out to the hardware and cancel all other
> pending jobs before destroying its context.

We do flush when file release in lima_ctx_mgr_fini. Why do we wait here
in flush? What's the difference?

> This prevents applications with multiple contexts from running into a
> race condition between running tasks and context destroy when
> terminating.
>
> Signed-off-by: Erico Nunes <nunes.erico at gmail.com>
> ---
>  drivers/gpu/drm/lima/lima_ctx.c | 18 ++++++++++++++++++
>  drivers/gpu/drm/lima/lima_ctx.h |  1 +
>  drivers/gpu/drm/lima/lima_drv.c | 17 ++++++++++++++++-
>  3 files changed, 35 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/lima/lima_ctx.c b/drivers/gpu/drm/lima/lima_ctx.c
> index 0e668fc1e0f9..e8fb5788ca69 100644
> --- a/drivers/gpu/drm/lima/lima_ctx.c
> +++ b/drivers/gpu/drm/lima/lima_ctx.c
> @@ -100,3 +100,21 @@ void lima_ctx_mgr_fini(struct lima_ctx_mgr *mgr)
>         xa_destroy(&mgr->handles);
>         mutex_destroy(&mgr->lock);
>  }
> +
> +long lima_ctx_mgr_flush(struct lima_ctx_mgr *mgr, long timeout)
> +{
> +       struct lima_ctx *ctx;
> +       unsigned long id;
> +
> +       mutex_lock(&mgr->lock);
> +       xa_for_each(&mgr->handles, id, ctx) {
> +               for (int i = 0; i < lima_pipe_num; i++) {
> +                       struct lima_sched_context *context = &ctx->context[i];
> +                       struct drm_sched_entity *entity = &context->base;
> +
> +                       timeout = drm_sched_entity_flush(entity, timeout);
> +               }
> +       }
> +       mutex_unlock(&mgr->lock);
> +       return timeout;
> +}
> diff --git a/drivers/gpu/drm/lima/lima_ctx.h b/drivers/gpu/drm/lima/lima_ctx.h
> index 5b1063ce968b..ff133db6ae4c 100644
> --- a/drivers/gpu/drm/lima/lima_ctx.h
> +++ b/drivers/gpu/drm/lima/lima_ctx.h
> @@ -30,5 +30,6 @@ struct lima_ctx *lima_ctx_get(struct lima_ctx_mgr *mgr, u32 id);
>  void lima_ctx_put(struct lima_ctx *ctx);
>  void lima_ctx_mgr_init(struct lima_ctx_mgr *mgr);
>  void lima_ctx_mgr_fini(struct lima_ctx_mgr *mgr);
> +long lima_ctx_mgr_flush(struct lima_ctx_mgr *mgr, long timeout);
>
>  #endif
> diff --git a/drivers/gpu/drm/lima/lima_drv.c b/drivers/gpu/drm/lima/lima_drv.c
> index 11ace5cebf4c..08169b0d9c28 100644
> --- a/drivers/gpu/drm/lima/lima_drv.c
> +++ b/drivers/gpu/drm/lima/lima_drv.c
> @@ -254,7 +254,22 @@ static const struct drm_ioctl_desc lima_drm_driver_ioctls[] = {
>         DRM_IOCTL_DEF_DRV(LIMA_CTX_FREE, lima_ioctl_ctx_free, DRM_RENDER_ALLOW),
>  };
>
> -DEFINE_DRM_GEM_FOPS(lima_drm_driver_fops);
> +static int lima_drm_driver_flush(struct file *filp, fl_owner_t id)
> +{
> +       struct drm_file *file = filp->private_data;
> +       struct lima_drm_priv *priv = file->driver_priv;
> +       long timeout = MAX_WAIT_SCHED_ENTITY_Q_EMPTY;
> +
> +       timeout = lima_ctx_mgr_flush(&priv->ctx_mgr, timeout);
> +
> +       return timeout >= 0 ? 0 : timeout;
> +}
> +
> +static const struct file_operations lima_drm_driver_fops = {
> +       .owner = THIS_MODULE,
> +       .flush = lima_drm_driver_flush,
> +       DRM_GEM_FOPS,
> +};
>
>  /*
>   * Changelog:
> --
> 2.49.0
>