Messages in this thread | | | Date | Thu, 2 Aug 2018 21:40:41 +0200 | From | Lukas Wunner <> | Subject | Re: [PATCH v4 8/8] drm/nouveau: Call pm_runtime_get_noresume() from hpd handlers |
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On Wed, Aug 01, 2018 at 05:14:58PM -0400, Lyude Paul wrote: > We can't and don't need to try resuming the device from our hotplug > handlers, but hotplug events are generally something we'd like to keep > the device awake for whenever possible. So, grab a PM ref safely in our > hotplug handlers using pm_runtime_get_noresume() and mark the device as > busy once we're finished.
Patch looks fine in principle, but doesn't seem to be sufficient to fix the following race:
1. runtime_suspend commences 2. user plugs in a display before the runtime_suspend worker disables hotplug interrupts in nouveau_display_fini() 3. hotplug is handled, display is lit up 4. runtime_suspend worker waits for hotplug handler to finish 5. GPU is runtime suspended and the newly plugged in display goes black
The call to pm_runtime_mark_last_busy() has no effect in this situation because rpm_suspend() doesn't look at the last_busy variable after the call to rpm_callback(). What's necessary here is that runtime_suspend is aborted and -EBUSY returned.
Thanks,
Lukas
> > Signed-off-by: Lyude Paul <lyude@redhat.com> > Cc: stable@vger.kernel.org > Cc: Lukas Wunner <lukas@wunner.de> > Cc: Karol Herbst <karolherbst@gmail.com> > --- > drivers/gpu/drm/nouveau/nouveau_connector.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/gpu/drm/nouveau/nouveau_connector.c b/drivers/gpu/drm/nouveau/nouveau_connector.c > index 8409c3f2c3a1..5a8e8c1ad647 100644 > --- a/drivers/gpu/drm/nouveau/nouveau_connector.c > +++ b/drivers/gpu/drm/nouveau/nouveau_connector.c > @@ -1152,6 +1152,11 @@ nouveau_connector_hotplug(struct nvif_notify *notify) > const char *name = connector->name; > struct nouveau_encoder *nv_encoder; > > + /* Resuming the device here isn't possible; but the suspend PM ops > + * will wait for us to finish our work before disabling us so this > + * should be enough > + */ > + pm_runtime_get_noresume(drm->dev->dev); > nv_connector->hpd_task = current; > > if (rep->mask & NVIF_NOTIFY_CONN_V0_IRQ) { > @@ -1171,6 +1176,9 @@ nouveau_connector_hotplug(struct nvif_notify *notify) > } > > nv_connector->hpd_task = NULL; > + > + pm_runtime_mark_last_busy(drm->dev->dev); > + pm_runtime_put_autosuspend(drm->dev->dev); > return NVIF_NOTIFY_KEEP; > } > > -- > 2.17.1 >
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