diff options
| author | Roland Dreier <rdreier@cisco.com> | 2009-02-06 17:48:09 -0800 |
|---|---|---|
| committer | Dave Airlie <airlied@redhat.com> | 2009-02-20 12:21:10 +1000 |
| commit | a35f2e2b83a789e189a501ebd722bc9a1310eb05 (patch) | |
| tree | a98654866d9295266dcf5ca61740004358b585ba /drivers | |
| parent | 96dec61d563fb8dff2c8427fdf85327a95b65c74 (diff) | |
drm/i915: Fix potential AB-BA deadlock in i915_gem_execbuffer()
Lockdep warns that i915_gem_execbuffer() can trigger a page fault (which
takes mmap_sem) while holding dev->struct_mutex, while drm_vm_open()
(which is called with mmap_sem already held) takes dev->struct_mutex.
So this is a potential AB-BA deadlock.
The way that i915_gem_execbuffer() triggers a page fault is by doing
copy_to_user() when returning new buffer offsets back to userspace;
however there is no reason to hold the struct_mutex when doing this
copy, since what is being copied is the contents of an array private to
i915_gem_execbuffer() anyway. So we can fix the potential deadlock (and
get rid of the lockdep warning) by simply moving the copy_to_user()
outside of where struct_mutex is held.
This fixes <http://bugzilla.kernel.org/show_bug.cgi?id=12491>.
Reported-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Dave Airlie <airlied@linux.ie>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/gpu/drm/i915/i915_gem.c | 21 |
1 files changed, 12 insertions, 9 deletions
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 55f4c060fa0..ff0d94dd355 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2634,15 +2634,6 @@ i915_gem_execbuffer(struct drm_device *dev, void *data, i915_verify_inactive(dev, __FILE__, __LINE__); - /* Copy the new buffer offsets back to the user's exec list. */ - ret = copy_to_user((struct drm_i915_relocation_entry __user *) - (uintptr_t) args->buffers_ptr, - exec_list, - sizeof(*exec_list) * args->buffer_count); - if (ret) - DRM_ERROR("failed to copy %d exec entries " - "back to user (%d)\n", - args->buffer_count, ret); err: for (i = 0; i < pinned; i++) i915_gem_object_unpin(object_list[i]); @@ -2652,6 +2643,18 @@ err: mutex_unlock(&dev->struct_mutex); + if (!ret) { + /* Copy the new buffer offsets back to the user's exec list. */ + ret = copy_to_user((struct drm_i915_relocation_entry __user *) + (uintptr_t) args->buffers_ptr, + exec_list, + sizeof(*exec_list) * args->buffer_count); + if (ret) + DRM_ERROR("failed to copy %d exec entries " + "back to user (%d)\n", + args->buffer_count, ret); + } + pre_mutex_err: drm_free(object_list, sizeof(*object_list) * args->buffer_count, DRM_MEM_DRIVER); |