[PATCH v2] drm/i915: Discard previous atomic state on resume if connectors change

[Lyude Paul]

no problem, I'll let you know when they're ready

On Mon, 2016-05-09 at 16:53 +0200, Daniel Vetter wrote:
> On Mon, May 09, 2016 at 10:07:08AM -0400, Lyude Paul wrote:
> > 
> > Yep, Dave's patches fix the issue on their own so this is only going to be
> > needed for 4.6.
> Ok, so not the first one that only needs to be applied to stable kernels.
> For that to work you need to explain that this is the most minimal fix for
> stabel kernels, and add a reference to the final commit in upstream that
> fixes the issue for real. Otherwise Greg KH won't take it. It still needs
> my ack.
> 
> Probably best to have an entire dp mst series for all of those, but maybe
> ping me first on irc so I can check them quickly before you hit send.
> -Daniel
> 
> > 
> > 
> > On Mon, 2016-05-09 at 08:42 +0200, Daniel Vetter wrote:
> > > 
> > > On Fri, May 06, 2016 at 05:39:56PM -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 before suspending is no longer valid, since it'll still be pointing to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
> > > > 
> > > > Cc: stable at vger.kernel.org
> > > > Signed-off-by: Lyude <cpaul at redhat.com>
> > > Is this still an issue on -nightly with the connector refcounting fixed?
> > > -Daniel
> > > 
> > > > 
> > > > 
> > > > ---
> > > >  drivers/gpu/drm/i915/intel_display.c | 12 ++++++++++++
> > > >  1 file changed, 12 insertions(+)
> > > > 
> > > > diff --git a/drivers/gpu/drm/i915/intel_display.c
> > > > b/drivers/gpu/drm/i915/intel_display.c
> > > > index 0f29ef6..d68efc7 100644
> > > > --- a/drivers/gpu/drm/i915/intel_display.c
> > > > +++ b/drivers/gpu/drm/i915/intel_display.c
> > > > @@ -15934,6 +15934,18 @@ void intel_display_resume(struct drm_device
> > > > *dev)
> > > >  retry:
> > > >  	ret = drm_modeset_lock_all_ctx(dev, &ctx);
> > > >  
> > > > +	/*
> > > > +	 * 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 (ret == 0 &&
> > > > +	    state->num_connector != dev->mode_config.num_connector) {
> > > > +		drm_atomic_state_free(state);
> > > > +		state = NULL;
> > > > +	}
> > > > +
> > > >  	if (ret == 0 && !setup) {
> > > >  		setup = true;
> > > >  
> > > > -- 
> > > > 2.5.5
> > > > 
> > > > _______________________________________________
> > > > dri-devel mailing list
> > > > dri-devel at lists.freedesktop.org
> > > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> > -- 
> > Cheers,
> > 	Lyude
> >