From d61a5c1063515e855bedb1b81e20e50b0ac3541e Mon Sep 17 00:00:00 2001

From: Lukas Wunner <lukas@wunner.de>

Date: Sun, 11 Feb 2018 10:38:28 +0100

Subject: [PATCH] drm/nouveau: Fix deadlock on runtime suspend

Git-commit: d61a5c1063515e855bedb1b81e20e50b0ac3541e

Patch-mainline: v4.16-rc3

References: bsc#1051510

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: 5addcf0a5f0f ("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

Acked-by: Takashi Iwai <tiwai@suse.de>

---

 drivers/gpu/drm/nouveau/nouveau_connector.c |   18 +++++++++++++-----

 1 file changed, 13 insertions(+), 5 deletions(-)

--- a/drivers/gpu/drm/nouveau/nouveau_connector.c

+++ b/drivers/gpu/drm/nouveau/nouveau_connector.c

@@ -570,9 +570,15 @@ nouveau_connector_detect(struct drm_conn

 		nv_connector->edid = NULL;

 	}

-	ret = pm_runtime_get_sync(connector->dev->dev);

-	if (ret < 0 && ret != -EACCES)

-		return conn_status;

+	/* 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) {

@@ -647,8 +653,10 @@ detect_analog:

  out:

-	pm_runtime_mark_last_busy(connector->dev->dev);

-	pm_runtime_put_autosuspend(connector->dev->dev);

+	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;

 }