Commit 9764951e authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Pin the pages first in shmem prepare read/write 



There is an improbable, but not impossible, case that if we leave the
pages unpin as we operate on the object, then somebody via the shrinker
may steal the lock (which lock? right now, it is struct_mutex, THE lock)
and change the cache domains after we have already inspected them.

(Whilst here, avail ourselves of the opportunity to take a couple of
steps to make the two functions look more similar.)

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160818161718.27187-11-chris@chris-wilson.co.uk
parent 3b5724d7

drivers/gpu/drm/i915/i915_gem.c

+28 −20
Original line number Diff line number Diff line
@@ -622,6 +622,12 @@ int i915_gem_obj_prepare_shmem_read(struct drm_i915_gem_object *obj, 
	if (ret)

		return ret;



	ret = i915_gem_object_get_pages(obj);

	if (ret)

		return ret;



	i915_gem_object_pin_pages(obj);



	i915_gem_object_flush_gtt_write_domain(obj);



	/* If we're not in the cpu read domain, set ourself into the gtt
@@ -633,22 +639,20 @@ int i915_gem_obj_prepare_shmem_read(struct drm_i915_gem_object *obj, 
		*needs_clflush = !cpu_cache_is_coherent(obj->base.dev,

							obj->cache_level);



	ret = i915_gem_object_get_pages(obj);

	if (ret)

		return ret;



	i915_gem_object_pin_pages(obj);



	if (*needs_clflush && !static_cpu_has(X86_FEATURE_CLFLUSH)) {

		ret = i915_gem_object_set_to_cpu_domain(obj, false);

		if (ret) {

			i915_gem_object_unpin_pages(obj);

			return ret;

		}

		if (ret)

			goto err_unpin;



		*needs_clflush = 0;

	}



	/* return with the pages pinned */

	return 0;



err_unpin:

	i915_gem_object_unpin_pages(obj);

	return ret;

}



int i915_gem_obj_prepare_shmem_write(struct drm_i915_gem_object *obj,
@@ -664,6 +668,12 @@ int i915_gem_obj_prepare_shmem_write(struct drm_i915_gem_object *obj, 
	if (ret)

		return ret;



	ret = i915_gem_object_get_pages(obj);

	if (ret)

		return ret;



	i915_gem_object_pin_pages(obj);



	i915_gem_object_flush_gtt_write_domain(obj);



	/* If we're not in the cpu write domain, set ourself into the
@@ -681,18 +691,11 @@ int i915_gem_obj_prepare_shmem_write(struct drm_i915_gem_object *obj, 
		*needs_clflush |= !cpu_cache_is_coherent(obj->base.dev,

							 obj->cache_level);



	ret = i915_gem_object_get_pages(obj);

	if (ret)

		return ret;



	i915_gem_object_pin_pages(obj);



	if (*needs_clflush && !static_cpu_has(X86_FEATURE_CLFLUSH)) {

		ret = i915_gem_object_set_to_cpu_domain(obj, true);

		if (ret) {

			i915_gem_object_unpin_pages(obj);

			return ret;

		}

		if (ret)

			goto err_unpin;



		*needs_clflush = 0;

	}
@@ -701,7 +704,12 @@ int i915_gem_obj_prepare_shmem_write(struct drm_i915_gem_object *obj, 


	intel_fb_obj_invalidate(obj, ORIGIN_CPU);

	obj->dirty = 1;

	/* return with the pages pinned */

	return 0;



err_unpin:

	i915_gem_object_unpin_pages(obj);

	return ret;

}



/* Per-page copy function for the shmem pread fastpath.

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