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由 Daniel Vetter 提交于
Originally it was impossible to be dropping the last refcount in this function since there was always one around still from the idr. But in commit 83f45fc3 Author: Daniel Vetter <daniel.vetter@ffwll.ch> Date: Wed Aug 6 09:10:18 2014 +0200 drm: Don't grab an fb reference for the idr we've switched to weak references, broke that assumption but forgot to fix it up. Since we still force-disable planes it's only possible to hit this when racing multiple rmfb with fbdev restoring or similar evil things. As long as userspace is nice it's impossible to hit the BUG_ON. But the BUG_ON would most likely be hit from fbdev code, which usually invovles the console_lock besides all modeset locks. So very likely we'd never get the bug reports if this was hit in the wild, hence better be safe than sorry and backport. Spotted by Matt Roper while reviewing other patches. [airlied: pull this back into 4.0 - the oops happens there] Cc: stable@vger.kernel.org Cc: Matt Roper <matthew.d.roper@intel.com> Reviewed-by: NMatt Roper <matthew.d.roper@intel.com> Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com> Signed-off-by: NDave Airlie <airlied@redhat.com>
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