[Intel-gfx] [PATCH 1/3] drm/modeset: Prime modeset lock vs dma_resv
Christian König
christian.koenig at amd.com
Wed Nov 20 08:34:03 UTC 2019
Am 19.11.19 um 22:08 schrieb Daniel Vetter:
> It's kinda really hard to get this wrong on a driver with both display
> and dma_resv locking. But who ever knows, so better to make sure that
> really all drivers nest these the same way.
>
> For actual lock semantics the acquire context nesting doesn't matter.
> But to teach lockdep what's going on with ww_mutex the acquire ctx is
> a fake lockdep lock, hence from a lockdep pov it does matter. That's
> why I figured better to include it.
>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Christian König <christian.koenig at amd.com>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
Why not add another __init function like we did for dma_resv? That
looked rather clean to me.
Either why feel free to add an Acked-by: Christian König
<christian.koenig at amd.com> to the patch.
Regards,
Christian.
> ---
> drivers/gpu/drm/drm_mode_config.c | 28 ++++++++++++++++++++++++++++
> 1 file changed, 28 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
> index 3b570a404933..08e6eff6a179 100644
> --- a/drivers/gpu/drm/drm_mode_config.c
> +++ b/drivers/gpu/drm/drm_mode_config.c
> @@ -27,6 +27,7 @@
> #include <drm/drm_file.h>
> #include <drm/drm_mode_config.h>
> #include <drm/drm_print.h>
> +#include <linux/dma-resv.h>
>
> #include "drm_crtc_internal.h"
> #include "drm_internal.h"
> @@ -415,6 +416,33 @@ void drm_mode_config_init(struct drm_device *dev)
> dev->mode_config.num_crtc = 0;
> dev->mode_config.num_encoder = 0;
> dev->mode_config.num_total_plane = 0;
> +
> + if (IS_ENABLED(CONFIG_LOCKDEP)) {
> + struct drm_modeset_acquire_ctx modeset_ctx;
> + struct ww_acquire_ctx resv_ctx;
> + struct dma_resv resv;
> + int ret;
> +
> + dma_resv_init(&resv);
> +
> + drm_modeset_acquire_init(&modeset_ctx, 0);
> + ret = drm_modeset_lock(&dev->mode_config.connection_mutex,
> + &modeset_ctx);
> + if (ret == -EDEADLK)
> + ret = drm_modeset_backoff(&modeset_ctx);
> +
> + ww_acquire_init(&resv_ctx, &reservation_ww_class);
> + ret = dma_resv_lock(&resv, &resv_ctx);
> + if (ret == -EDEADLK)
> + dma_resv_lock_slow(&resv, &resv_ctx);
> +
> + dma_resv_unlock(&resv);
> + ww_acquire_fini(&resv_ctx);
> +
> + drm_modeset_drop_locks(&modeset_ctx);
> + drm_modeset_acquire_fini(&modeset_ctx);
> + dma_resv_fini(&resv);
> + }
> }
> EXPORT_SYMBOL(drm_mode_config_init);
>
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