[PATCH] Input: omap-keypad - fix runtime pm imbalance on error

[PATCH] Input: omap-keypad - fix runtime pm imbalance on error

[Dinghao Liu]

pm_runtime_get_sync() increments the runtime PM usage counter even
the call returns an error code. Thus a pairing decrement is needed
on the error handling path to keep the counter balanced.

Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
---
 drivers/input/keyboard/omap4-keypad.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/input/keyboard/omap4-keypad.c b/drivers/input/keyboard/omap4-keypad.c
index 94c94d7f5155..d13d81c796d2 100644
--- a/drivers/input/keyboard/omap4-keypad.c
+++ b/drivers/input/keyboard/omap4-keypad.c
@@ -371,8 +371,8 @@ static int omap4_keypad_probe(struct platform_device *pdev)
 err_free_input:
 	input_free_device(input_dev);
 err_pm_put_sync:
-	pm_runtime_put_sync(&pdev->dev);
 err_unmap:
+	pm_runtime_put_sync(&pdev->dev);
 	iounmap(keypad_data->base);
 err_release_mem:
 	release_mem_region(res->start, resource_size(res));
-- 
2.17.1

Re: [PATCH] Input: omap-keypad - fix runtime pm imbalance on error

[Dmitry Torokhov]

Hi Dinghao,

On Wed, May 20, 2020 at 6:35 AM Dinghao Liu <dinghao.liu@zju.edu.cn> wrote:
>
> pm_runtime_get_sync() increments the runtime PM usage counter even
> the call returns an error code. Thus a pairing decrement is needed
> on the error handling path to keep the counter balanced.

This is a very surprising behavior and I wonder if this should be
fixed in the PM core (or the required cleanup steps need to be called
out in the function description). I also see that a few drivers that
handle this situation correctly (?) call pm_runtime_put_noidle()
instead of pm_runtime_put_sync() in the error path.

Rafael, do you have any guidance here?

Thanks.

-- 
Dmitry

Re: [PATCH] Input: omap-keypad - fix runtime pm imbalance on error

[Rafael J. Wysocki]

On Wed, May 20, 2020 at 7:02 PM Dmitry Torokhov
<dmitry.torokhov@gmail.com> wrote:
>
> Hi Dinghao,
>
> On Wed, May 20, 2020 at 6:35 AM Dinghao Liu <dinghao.liu@zju.edu.cn> wrote:
> >
> > pm_runtime_get_sync() increments the runtime PM usage counter even
> > the call returns an error code. Thus a pairing decrement is needed
> > on the error handling path to keep the counter balanced.
>
> This is a very surprising behavior and I wonder if this should be
> fixed in the PM core (or the required cleanup steps need to be called
> out in the function description).

It has been like that forever and it's intentional, because it allows
certain pieces of code to do things like

pm_runtime_get_sync(dev);
/* do something regardless of whether or not PM-runtime is enabled for dev */
pm_runtime_put(dev);

So I wouldn't really call it surprising.

> I also see that a few drivers that
> handle this situation correctly (?) call pm_runtime_put_noidle()
> instead of pm_runtime_put_sync() in the error path.
>
> Rafael, do you have any guidance here?

Feel free to improve the kerneldoc comment of __pm_runtime_resume(),
although it is clear enough to me, and fix the callers that leak the
refcount.

Re: Re: [PATCH] Input: omap-keypad - fix runtime pm imbalance on error

[dinghao.liu]

Fixing this in the PM core will influence all callers of pm_runtime_get_sync().
Therefore I think the better solution is to fix its misused callers.

Regards,
Dinghao

"Dmitry Torokhov" <dmitry.torokhov@gmail.com>写道：
> Hi Dinghao,
> 
> On Wed, May 20, 2020 at 6:35 AM Dinghao Liu <dinghao.liu@zju.edu.cn> wrote:
> >
> > pm_runtime_get_sync() increments the runtime PM usage counter even
> > the call returns an error code. Thus a pairing decrement is needed
> > on the error handling path to keep the counter balanced.
> 
> This is a very surprising behavior and I wonder if this should be
> fixed in the PM core (or the required cleanup steps need to be called
> out in the function description). I also see that a few drivers that
> handle this situation correctly (?) call pm_runtime_put_noidle()
> instead of pm_runtime_put_sync() in the error path.
> 
> Rafael, do you have any guidance here?
> 
> Thanks.
> 
> -- 
> Dmitry