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@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Cc: Lukas Wunner <lukas@xxxxxxxxx>
> Cc: Karol Herbst <karolherbst@xxxxxxxxx>
> ---
> 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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