[Intel-gfx] [PATCH] drm/i915: Discard previous atomic state on resume if connectors change

[Lyude Paul]

Yeah airlied said the same thing. This patch is more intended for just 4.6 since
the refcounting patch isn't very likely to get into 4.6.

On Tue, 2016-05-03 at 16:29 +0200, Daniel Vetter wrote:
> 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 before suspending is no longer valid, since it'll still be pointing to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 at vger.kernel.org
> > Signed-off-by: Lyude <cpaul at redhat.com>
> 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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