Hi Zhang,
On Tue, Nov 10, 2020 at 10:29 AM Zhang Qilong <zhangqilo...@huawei.com> wrote:
> In many case, we need to check return value of pm_runtime_get_sync, but
> it brings a trouble to the usage counter processing. Many callers forget
> to decrease the usage counter when it failed, which could resulted in
> reference leak. It has been discussed a lot[0][1]. So we add a function
> to deal with the usage counter for better coding.
>
> [0]https://lkml.org/lkml/2020/6/14/88
> [1]https://patchwork.ozlabs.org/project/linux-tegra/list/?series=178139
> Signed-off-by: Zhang Qilong <zhangqilo...@huawei.com>
Thanks for your patch, which is now commit dd8088d5a8969dc2 ("PM:
runtime: Add pm_runtime_resume_and_get to deal with usage counter") in
v5.10-rc5.
> --- a/include/linux/pm_runtime.h
> +++ b/include/linux/pm_runtime.h
> @@ -386,6 +386,27 @@ static inline int pm_runtime_get_sync(struct device *dev)
> return __pm_runtime_resume(dev, RPM_GET_PUT);
> }
>
> +/**
> + * pm_runtime_resume_and_get - Bump up usage counter of a device and resume
> it.
> + * @dev: Target device.
> + *
> + * Resume @dev synchronously and if that is successful, increment its runtime
> + * PM usage counter. Return 0 if the runtime PM usage counter of @dev has
> been
> + * incremented or a negative error code otherwise.
> + */
> +static inline int pm_runtime_resume_and_get(struct device *dev)
Perhaps this function should be called pm_runtime_resume_and_get_sync(),
to make it clear it does a synchronous get?
I had to look into the implementation to verify that a change like
- ret = pm_runtime_get_sync(&pdev->dev);
+ ret = pm_runtime_resume_and_get(&pdev->dev);
in the follow-up patches is actually a valid change, maintaining
synchronous operation. Oh, pm_runtime_resume() is synchronous, too...
While I agree the old pm_runtime_get_sync() had confusing semantics, we
should go to great lengths to avoid making the same mistake while fixing
it.
> +{
> + int ret;
> +
> + ret = __pm_runtime_resume(dev, RPM_GET_PUT);
> + if (ret < 0) {
> + pm_runtime_put_noidle(dev);
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> /**
> * pm_runtime_put - Drop device usage counter and queue up "idle check" if 0.
> * @dev: Target device.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
