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 before suspending is no longer valid, since it'll still be pointing to 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@xxxxxxxxxxxxxxx > Signed-off-by: Lyude <cpaul@xxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html