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drm/nouveau: Fix deadlock on runtime suspend
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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@ -570,9 +570,15 @@ nouveau_connector_detect(struct drm_connector *connector, bool force)
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nv_connector->edid = NULL;
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}
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ret = pm_runtime_get_sync(connector->dev->dev);
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if (ret < 0 && ret != -EACCES)
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return conn_status;
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/* Outputs are only polled while runtime active, so acquiring a
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* runtime PM ref here is unnecessary (and would deadlock upon
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* runtime suspend because it waits for polling to finish).
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*/
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if (!drm_kms_helper_is_poll_worker()) {
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ret = pm_runtime_get_sync(connector->dev->dev);
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if (ret < 0 && ret != -EACCES)
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return conn_status;
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}
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nv_encoder = nouveau_connector_ddc_detect(connector);
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if (nv_encoder && (i2c = nv_encoder->i2c) != NULL) {
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@ -647,8 +653,10 @@ detect_analog:
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out:
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pm_runtime_mark_last_busy(connector->dev->dev);
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pm_runtime_put_autosuspend(connector->dev->dev);
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if (!drm_kms_helper_is_poll_worker()) {
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pm_runtime_mark_last_busy(connector->dev->dev);
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pm_runtime_put_autosuspend(connector->dev->dev);
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}
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return conn_status;
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}
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