forked from luck/tmp_suning_uos_patched
a35f2e2b83
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> |
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