Hi Greg, On Mon, Feb 26, 2018 at 05:07:55PM +0100, gregkh@xxxxxxxxxxxxxxxxxxx wrote: > The patch below does not apply to the 4.14-stable tree. The patch applies just fine, but it has two prerequisites, as specified in the commit message: Cc: stable@xxxxxxxxxxxxxxx # v3.12+: 27d4ee03078a: workqueue: Allow retrieval of current task's work struct Cc: stable@xxxxxxxxxxxxxxx # v3.12+: 25c058ccaf2e: drm: Allow determining if current task is output poll worker The radeon and amdgpu patches have the same prerequisites. Thanks, Lukas > If someone wants it applied there, or to any other stable or longterm > tree, then please email the backport, including the original git commit > id to <stable@xxxxxxxxxxxxxxx>. > > thanks, > > greg k-h > > ------------------ original commit in Linus's tree ------------------ > > From d61a5c1063515e855bedb1b81e20e50b0ac3541e Mon Sep 17 00:00:00 2001 > From: Lukas Wunner <lukas@xxxxxxxxx> > Date: Sun, 11 Feb 2018 10:38:28 +0100 > Subject: [PATCH] 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: 5addcf0a5f0f ("nouveau: add runtime PM support (v0.9)") > Cc: stable@xxxxxxxxxxxxxxx # v3.12+: 27d4ee03078a: workqueue: Allow retrieval of current task's work struct > Cc: stable@xxxxxxxxxxxxxxx # v3.12+: 25c058ccaf2e: drm: Allow determining if current task is output poll worker > Cc: Ben Skeggs <bskeggs@xxxxxxxxxx> > Cc: Dave Airlie <airlied@xxxxxxxxxx> > Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx> > Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx> > Link: https://patchwork.freedesktop.org/patch/msgid/b7d2cbb609a80f59ccabfdf479b9d5907c603ea1.1518338789.git.lukas@xxxxxxxxx > > diff --git a/drivers/gpu/drm/nouveau/nouveau_connector.c b/drivers/gpu/drm/nouveau/nouveau_connector.c > index 69d6e61a01ec..6ed9cb053dfa 100644 > --- 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_connector *connector, bool force) > 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 @@ nouveau_connector_detect(struct drm_connector *connector, bool force) > > 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; > } >