netdev - 答复: [PATCH v2 1/2] PM: runtime: Add a general runtime get sync operation to deal with usage counter

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Message-ID: <446df7a9d66f4eb08f5971fba7dca1db@huawei.com>
Date:   Mon, 9 Nov 2020 16:15:00 +0000
From:   zhangqilong <zhangqilong3@...wei.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
CC:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "fugang.duan@....com" <fugang.duan@....com>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>
Subject: 答复: [PATCH v2 1/2] PM: runtime: Add a general runtime get sync operation to deal with usage counter

Hi

> 
> On Mon, Nov 9, 2020 at 4:50 PM zhangqilong <zhangqilong3@...wei.com>
> wrote:
> >
> > > operation to deal with usage counter
> > >
> > > On Mon, Nov 9, 2020 at 4:00 PM Zhang Qilong
> > > <zhangqilong3@...wei.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. 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/patch/20200520
> > > > 0951 48.10995-1-dinghao.liu@....edu.cn/
> > > > Signed-off-by: Zhang Qilong <zhangqilong3@...wei.com>
> > > > ---
> > > >  include/linux/pm_runtime.h | 30 ++++++++++++++++++++++++++++++
> > > >  1 file changed, 30 insertions(+)
> > > >
> > > > diff --git a/include/linux/pm_runtime.h
> > > > b/include/linux/pm_runtime.h index 4b708f4e8eed..6549ce764400
> > > > 100644
> > > > --- a/include/linux/pm_runtime.h
> > > > +++ b/include/linux/pm_runtime.h
> > > > @@ -386,6 +386,36 @@ static inline int pm_runtime_get_sync(struct
> > > > device
> > > *dev)
> > > >         return __pm_runtime_resume(dev, RPM_GET_PUT);  }
> > > >
> > > > +/**
> > > > + * pm_runtime_general_get - Bump up usage counter of a device and
> > > resume it.
> > > > + * @dev: Target device.
> > > > + *
> > > > + * Increase runtime PM usage counter of @dev first, and carry out
> > > > +runtime-resume
> > > > + * of it synchronously. If __pm_runtime_resume return negative
> > > > +value(device is in
> > > > + * error state), we to need decrease the usage counter before it
> > > > +return. If
> > > > + * __pm_runtime_resume return positive value, it means the
> > > > +runtime of device has
> > > > + * already been in active state, and we let the new wrapper
> > > > +return zero
> > > instead.
> > > > + *
> > > > + * The possible return values of this function is zero or negative value.
> > > > + * zero:
> > > > + *    - it means resume succeeed or runtime of device has already been
> > > active, the
> > > > + *      runtime PM usage counter of @dev remains incremented.
> > > > + * negative:
> > > > + *    - it means failure and the runtime PM usage counter of @dev has
> > > been balanced.
> > >
> > > The kerneldoc above is kind of noisy and it is hard to figure out
> > > what the helper really does from it.
> > >
> > > You could basically say something like "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."
> > >
> >
> > How about the following description.
> > /**
> > 390  * pm_runtime_general_get - Bump up usage counter of a device and
> resume it.
> > 391  * @dev: Target device.
> > 392  *
> > 393  * Increase runtime PM usage counter of @dev first, and carry out
> > runtime-resume
> > 394  * of it synchronously. If __pm_runtime_resume return negative
> > value(device is in
> > 395  * error state), we to need decrease the usage counter before it
> > return. If
> > 396  * __pm_runtime_resume return positive value, it means the runtime
> > of device has
> > 397  * already been in active state, and we let the new wrapper return zero
> instead.
> > 398  *
> 
> If you add the paragraph below, the one above becomes redundant IMV.
> 
> > 399  * Resume @dev synchronously and if that is successful, and
> > increment its runtime
> 
> "Resume @dev synchronously and if that is successful, increment its runtime"
> 
> (drop the extra "and").
> 
> > 400  * PM usage counter if it turn out to equal to 0. The runtime PM
> > usage counter of
> 
> The "if it turn out to equal to 0" phrase is redundant (and the grammar in it is
> incorrect).
> 
> > 401  * @dev has been incremented or a negative error code otherwise.
> > 402  */
> 
> Why don't you use what I said verbatim?

I had misunderstand just now, sorry for that. The description is as follows:
389 /**
390  * pm_runtime_resume_and_get - Bump up usage counter of a device and resume it.
391  * @dev: Target device.
392  *
393  * Resume @dev synchronously if that is successful, increment its runtime PM
394  * usage counter.  Return 0 if the runtime PM usage counter of @dev has been
395  * incremented or a negative error code otherwise.
396  */

Do you think it's OK?

Thanks,
Zhang