On Tue, May 03, 2016 at 10:03:40AM -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 before suspending is no longer valid, since it'll still be pointing to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
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Lyude <cpaul@xxxxxxxxxx>
This should be addressed by the connector refcounting fixes Dave Airlie
has for 4.7 (not all merged yet though). Can you please retest with those?
-Daniel
> ---
> drivers/gpu/drm/i915/intel_display.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 6e0d828..252c06c 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -15945,6 +15945,17 @@ void intel_display_resume(struct drm_device *dev)
> dev_priv->modeset_restore_state = NULL;
>
> /*
> + * With MST, the number of connectors can change between suspend and
> + * resume, which means that the state we want to restore might now be
> + * impossible to use since it'll be pointing to non-existant
> + * connectors.
> + */
> + if (state->num_connector != dev->mode_config.num_connector) {
> + drm_atomic_state_free(state);
> + state = NULL;
> + }
> +
> + /*
> * This is a cludge because with real atomic modeset mode_config.mutex
> * won't be taken. Unfortunately some probed state like
> * audio_codec_enable is still protected by mode_config.mutex, so lock
> --
> 2.5.5
>
> _______________________________________________
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--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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