linux-kernel - Re: [PATCH v7 2/3] trivial: PM / Hibernate: clean up checkpatch in hibernate.c

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Date:	Tue, 04 Feb 2014 15:45:49 -0800
From:	Joe Perches <joe@...ches.com>
To:	Sebastian Capella <sebastian.capella@...aro.org>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-pm@...r.kernel.org, linaro-kernel@...ts.linaro.org,
	patches@...aro.org, Pavel Machek <pavel@....cz>,
	Len Brown <len.brown@...el.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH v7 2/3] trivial: PM / Hibernate: clean up checkpatch in
 hibernate.c

On Tue, 2014-02-04 at 14:05 -0800, Sebastian Capella wrote:
> Quoting Joe Perches (2014-02-04 13:21:02)
> > On Tue, 2014-02-04 at 12:43 -0800, Sebastian Capella wrote:
> > > Checkpatch reports several warnings in hibernate.c
> > > printk use removed, long lines wrapped, whitespace cleanup,
> > > extend short msleeps, while loops on two lines.
> > []
> > > diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> > []
> > > @@ -765,7 +762,7 @@ static int software_resume(void)
> > >       if (isdigit(resume_file[0]) && resume_wait) {
> > >               int partno;
> > >               while (!get_gendisk(swsusp_resume_device, &partno))
> > > -                     msleep(10);
> > > +                     msleep(20);
> > 
> > What good is changing this from 10 to 20?
> > 
> > > @@ -776,8 +773,9 @@ static int software_resume(void)
> > >               wait_for_device_probe();
> > >  
> > >               if (resume_wait) {
> > > -                     while ((swsusp_resume_device = name_to_dev_t(resume_file)) == 0)
> > > -                             msleep(10);
> > > +                     while ((swsusp_resume_device =
> > > +                                     name_to_dev_t(resume_file)) == 0)
> > > +                             msleep(20);
> > 
> > here too.
> 
> Thanks Joe!
> 
> I'm happy to make whatever change is best.  I just ran into one
> checkpatch warning around a printk I indented and figured I'd try to get
> them all if I could.

Shutting up checkpatch for the sake of shutting of
checkpatch is sometimes not the right thing to do.

> The delays in question didn't appear timing critical as both are looping
> waiting for device discovery to complete.  They're only enabled when using
> the resumewait command line parameter.

Any time it happens faster doesn't hurt and
can therefore could resume faster no?

> Is this an incorrect checkpatch warning?  The message from checkpatch
> implies using msleep for smaller values can be misleading.

That's true, but it doesn't mean it's required
to change the code.

>   - Why not msleep for (1ms - 20ms)?                               
>     Explained originally here:                               
>       http://lkml.org/lkml/2007/8/3/250                
>     msleep(1~20) may not do what the caller intends, and     
>     will often sleep longer (~20 ms actual sleep for any     
>     value given in the 1~20ms range). In many cases this     
>     is not the desired behavior. 
> 
> When I look at kernel/timers.c in my current kernel, I see msleep is
> using msecs_to_jiffies + 1, and on my current platform this appears to
> be ~20msec as the jiffies are 10ms.

And on platforms where HZ is 1000, it's
still slightly faster.

I'd just leave it alone.

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