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drm/modeset: Prime modeset lock vs dma_resv

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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@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Christian König <christian.koenig@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191119210844.16947-2-daniel.vetter@ffwll.ch
This commit is contained in:
Daniel Vetter 2019-11-19 22:08:42 +01:00
parent 7819c4607f
commit 2c51419e8c
1 changed files with 28 additions and 0 deletions
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28
drivers/gpu/drm/drm_mode_config.c
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@ -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);