Commit 24f82eef authored Feb 11, 2018 by Lukas Wunner Committed by Greg Kroah-Hartman Mar 18, 2018

drm/nouveau: Fix deadlock on runtime suspend

commit d61a5c1063515e855bedb1b81e20e50b0ac3541e upstream.

nouveau's ->runtime_suspend hook calls drm_kms_helper_poll_disable(),
which waits for the output poll worker to finish if it's running.

The output poll worker meanwhile calls pm_runtime_get_sync() in
nouveau_connector_detect() which waits for the ongoing suspend to finish,
causing a deadlock.

Fix by not acquiring a runtime PM ref if nouveau_connector_detect() is
called in the output poll worker's context.  This is safe because
the poll worker is only enabled while runtime active and we know that
->runtime_suspend waits for it to finish.

Other contexts calling nouveau_connector_detect() do require a runtime
PM ref, these comprise:

  status_store() drm sysfs interface
  ->fill_modes drm callback
  drm_fb_helper_probe_connector_modes()
  drm_mode_getconnector()
  nouveau_connector_hotplug()
  nouveau_display_hpd_work()
  nv17_tv_set_property()

Stack trace for posterity:

  INFO: task kworker/0:1:58 blocked for more than 120 seconds.
  Workqueue: events output_poll_execute [drm_kms_helper]
  Call Trace:
   schedule+0x28/0x80
   rpm_resume+0x107/0x6e0
   __pm_runtime_resume+0x47/0x70
   nouveau_connector_detect+0x7e/0x4a0 [nouveau]
   nouveau_connector_detect_lvds+0x132/0x180 [nouveau]
   drm_helper_probe_detect_ctx+0x85/0xd0 [drm_kms_helper]
   output_poll_execute+0x11e/0x1c0 [drm_kms_helper]
   process_one_work+0x184/0x380
   worker_thread+0x2e/0x390

  INFO: task kworker/0:2:252 blocked for more than 120 seconds.
  Workqueue: pm pm_runtime_work
  Call Trace:
   schedule+0x28/0x80
   schedule_timeout+0x1e3/0x370
   wait_for_completion+0x123/0x190
   flush_work+0x142/0x1c0
   nouveau_pmops_runtime_suspend+0x7e/0xd0 [nouveau]
   pci_pm_runtime_suspend+0x5c/0x180
   vga_switcheroo_runtime_suspend+0x1e/0xa0
   __rpm_callback+0xc1/0x200
   rpm_callback+0x1f/0x70
   rpm_suspend+0x13c/0x640
   pm_runtime_work+0x6e/0x90
   process_one_work+0x184/0x380
   worker_thread+0x2e/0x390

Bugzilla: https://bugs.archlinux.org/task/53497
Bugzilla: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=870523
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=70388#c33


Fixes: 5addcf0a ("nouveau: add runtime PM support (v0.9)")
Cc: stable@vger.kernel.org # v3.12+: 27d4ee03078a: workqueue: Allow retrieval of current task's work struct
Cc: stable@vger.kernel.org # v3.12+: 25c058ccaf2e: drm: Allow determining if current task is output poll worker
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Dave Airlie <airlied@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://patchwork.freedesktop.org/patch/msgid/b7d2cbb609a80f59ccabfdf479b9d5907c603ea1.1518338789.git.lukas@wunner.de


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent d006d904

drivers/gpu/drm/nouveau/nouveau_connector.c

+13 −5

Original line number	Diff line number	Diff line
		@@ -271,9 +271,15 @@ nouveau_connector_detect(struct drm_connector *connector, bool force)
		nv_connector->edid = NULL;
		}

		/* Outputs are only polled while runtime active, so acquiring a
		* runtime PM ref here is unnecessary (and would deadlock upon
		* runtime suspend because it waits for polling to finish).
		*/
		if (!drm_kms_helper_is_poll_worker()) {
		ret = pm_runtime_get_sync(connector->dev->dev);
		if (ret < 0 && ret != -EACCES)
		return conn_status;
		}

		nv_encoder = nouveau_connector_ddc_detect(connector);
		if (nv_encoder && (i2c = nv_encoder->i2c) != NULL) {
		@@ -348,8 +354,10 @@ nouveau_connector_detect(struct drm_connector *connector, bool force)

		out:

		if (!drm_kms_helper_is_poll_worker()) {
		pm_runtime_mark_last_busy(connector->dev->dev);
		pm_runtime_put_autosuspend(connector->dev->dev);
		}

		return conn_status;
		}