On Tue, May 31, 2016 at 12:49:06PM -0400, Lyude wrote: > If an MST device is disconnected while the machine is suspended, the > number of connectors will change as well after we call > intel_dp_mst_resume(). This means that any previous atomic state we had > before suspending is no longer valid, since it'll still be pointing to > missing connectors. We need to check for this before committing the > state, otherwise we'll kernel panic on resume whenever if any MST > display was disconnected before we started resuming: > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 > IP: [<ffffffffa01588ef>] drm_atomic_helper_check_modeset+0x29f/0xb40 [drm_kms_helper] > Call Trace: > [<ffffffffa02354f4>] intel_atomic_check+0x34/0x1180 [i915] > [<ffffffff810e6c3f>] ? mark_held_locks+0x6f/0xa0 > [<ffffffff810e6d99>] ? trace_hardirqs_on_caller+0x129/0x1b0 > [<ffffffffa00ff1d2>] drm_atomic_check_only+0x192/0x620 [drm] > [<ffffffff813ee001>] ? pci_pm_thaw+0x21/0x90 > [<ffffffffa00ff677>] drm_atomic_commit+0x17/0x60 [drm] > [<ffffffffa023e0ad>] intel_display_resume+0xbd/0x160 [i915] > [<ffffffff813ee070>] ? pci_pm_thaw+0x90/0x90 > [<ffffffffa01b60d8>] i915_drm_resume+0xd8/0x160 [i915] > [<ffffffffa01b6185>] i915_pm_resume+0x25/0x30 [i915] > [<ffffffff813ee0d4>] pci_pm_resume+0x64/0xa0 > [<ffffffff814d9ea0>] dpm_run_callback+0x90/0x190 > [<ffffffff814da455>] device_resume+0xd5/0x1f0 > [<ffffffff814da58d>] async_resume+0x1d/0x50 > [<ffffffff810b6718>] async_run_entry_fn+0x48/0x150 > [<ffffffff810acc19>] process_one_work+0x1e9/0x5c0 > [<ffffffff810acb96>] ? process_one_work+0x166/0x5c0 > [<ffffffff810ad038>] worker_thread+0x48/0x4e0 > [<ffffffff810acff0>] ? process_one_work+0x5c0/0x5c0 > [<ffffffff810b3794>] kthread+0xe4/0x100 > [<ffffffff81742672>] ret_from_fork+0x22/0x50 > [<ffffffff810b36b0>] ? kthread_create_on_node+0x200/0x200 > > Changes since v1: > - Move drm_atomic_state_free() call down so we're holding the > appropriate locks when destroying the atomic state > Changes since v2: > - Check that state != NULL before we start accessing it's members > > This fix is only required for 4.6 and below. David Airlie's patchseries > for 4.7 to add connector reference counting provides a more proper fix > for this. This doesn't apply to 4.5-stable or 4.4-stable, if you want it there, can you provide a backported version for me to apply? thanks, greg k-h _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
