[Nouveau] [PATCH 1/9] drm/nouveau: Don't leak runtime pm ref on driver unload

[Peter Wu]

On Tue, May 24, 2016 at 06:03:27PM +0200, Lukas Wunner wrote:
> nouveau_drm_load() calls pm_runtime_put() if nouveau_runtime_pm != 0,
> but nouveau_drm_unload() calls pm_runtime_get_sync() unconditionally.
> We therefore leak a runtime pm ref whenever nouveau is loaded with
> runpm=0 and then unloaded. The GPU will subsequently never runtime
> suspend even if nouveau is loaded again with runpm=1.
> 
> Fix by taking the runtime pm ref under the same condition that it was
> released on driver load.
> 
> Fixes: 5addcf0a5f0f ("nouveau: add runtime PM support (v0.9)")
> Cc: Dave Airlie <airlied at redhat.com>
> Reported-by: Karol Herbst <nouveau at karolherbst.de>
> Tested-by: Karol Herbst <nouveau at karolherbst.de>
> Signed-off-by: Lukas Wunner <lukas at wunner.de>

Looks good, I tested this scenario:

    ru(){ cat /sys/bus/pci/devices/0000\:01:00.0/power/runtime_usage;}
    ru # reports 1
    modprobe nouveau runpm=0
    ru # reports 2
    rmmod nouveau
    ru # reports 1

Without runpm=0 the count drops to 0 in the second step and stays 0 in
the third step. After applying patch 2/9, this correctly reports 1 as
expected (this is the same as manually setting power/control to on).

Peter

> ---
>  drivers/gpu/drm/nouveau/nouveau_drm.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c
> index 11f8dd9..faf7438 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_drm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
> @@ -498,7 +498,10 @@ nouveau_drm_unload(struct drm_device *dev)
>  {
>  	struct nouveau_drm *drm = nouveau_drm(dev);
>  
> -	pm_runtime_get_sync(dev->dev);
> +	if (nouveau_runtime_pm != 0) {
> +		pm_runtime_get_sync(dev->dev);
> +	}
> +
>  	nouveau_fbcon_fini(dev);
>  	nouveau_accel_fini(drm);
>  	nouveau_hwmon_fini(dev);
> -- 
> 2.8.1
> 
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-- 
Kind regards,
Peter Wu
https://lekensteyn.nl