3.16.57-rc1 review patch. If anyone has any objections, please let me know.
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From: Lukas Wunner lukas@wunner.de
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: 5addcf0a5f0f ("nouveau: add runtime PM support (v0.9)") 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/b7d2cbb609a80f59ccabfdf479b9d5... Signed-off-by: Ben Hutchings ben@decadent.org.uk --- 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 @@ -256,9 +256,15 @@ 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) { @@ -326,8 +332,10 @@ 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; }