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: 5addcf0a5f ("nouveau: add runtime PM support (v0.9)")
Cc: stable@vger.kernel.org # v3.12+: 27d4ee0307: workqueue: Allow retrieval of current task's work struct
Cc: stable@vger.kernel.org # v3.12+: 25c058ccaf: 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
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