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

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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: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160818161718.27187-11-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2016-08-18 17:16:50 +01:00
parent 3b5724d702
commit 9764951e7f
1 changed files with 28 additions and 20 deletions
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48
drivers/gpu/drm/i915/i915_gem.c
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@ -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.