path: root/drivers/gpu/drm
diff options
authorChris Wilson <chris@chris-wilson.co.uk>2011-03-14 15:11:24 +0000
committerGreg Kroah-Hartman <gregkh@suse.de>2011-03-27 11:36:30 -0700
commitd449b2a924941d023fb9dc1ad397c5b4b740aba4 (patch)
treef06208e76373adb54764383a00b864ad38a16d3d /drivers/gpu/drm
parentde3da06e17ed82edfefef6cca8116548828f45b4 (diff)
drm/i915: Disable pagefaults along execbuffer relocation fast path
commit d4aeee776017b6da6dcd12f453cd82a3c951a0dc upstream. Along the fast path for relocation handling, we attempt to copy directly from the user data structures whilst holding our mutex. This causes lockdep to warn about circular lock dependencies if we need to pagefault the user pages. [Since when handling a page fault on a mmapped bo, we need to acquire the struct mutex whilst already holding the mm semaphore, it is then verboten to acquire the mm semaphore when already holding the struct mutex. The likelihood of the user passing in the relocations contained in a GTT mmaped bo is low, but conceivable for extreme pathology.] In order to force the mm to return EFAULT rather than handle the pagefault, we therefore need to disable pagefaults across the relocation fast path. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/gpu/drm')
1 files changed, 17 insertions, 4 deletions
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 50ab1614571..ded73a6007a 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -388,6 +388,10 @@ i915_gem_execbuffer_relocate_entry(struct drm_i915_gem_object *obj,
uint32_t __iomem *reloc_entry;
void __iomem *reloc_page;
+ /* We can't wait for rendering with pagefaults disabled */
+ if (obj->active && in_atomic())
+ return -EFAULT;
ret = i915_gem_object_set_to_gtt_domain(obj, 1);
if (ret)
return ret;
@@ -461,15 +465,24 @@ i915_gem_execbuffer_relocate(struct drm_device *dev,
struct list_head *objects)
struct drm_i915_gem_object *obj;
- int ret;
+ int ret = 0;
+ /* This is the fast path and we cannot handle a pagefault whilst
+ * holding the struct mutex lest the user pass in the relocations
+ * contained within a mmaped bo. For in such a case we, the page
+ * fault handler would call i915_gem_fault() and we would try to
+ * acquire the struct mutex again. Obviously this is bad and so
+ * lockdep complains vehemently.
+ */
+ pagefault_disable();
list_for_each_entry(obj, objects, exec_list) {
ret = i915_gem_execbuffer_relocate_object(obj, eb);
if (ret)
- return ret;
+ break;
+ pagefault_enable();
- return 0;
+ return ret;
static int