linux-kernel - Re: [PATCH] staging: nokia_h4: nokia_core.c: use usleep

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Message-ID: <CAMGgR5ui-4+7-VKSpJ5_NukbkuxK1sRWg0RsS=Ai+Vs2xn119A@mail.gmail.com>
Date:	Fri, 30 May 2014 13:58:02 +0100
From:	Miguel Oliveira <cmroliv@...il.com>
To:	Pavel Machek <pavel@....cz>
Cc:	gregkh@...uxfoundation.org,
	Gülşah Köse <gulsah.1004@...il.com>,
	pali.rohar@...il.com, peter.p.waskiewicz.jr@...el.com,
	Kristina Martšenko <kristina.martsenko@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: nokia_h4: nokia_core.c: use usleep_range()
 instead of msleep()

Not on my prespective. Its says "~20 ms actual sleep for any value
given in the 1~20ms range", so from my point of view it will sleep for
20ms, so I will save between 5 to 10ms. But maybe I'm seeing it the
wrong way.


Regards

2014-05-30 13:35 GMT+01:00 Pavel Machek <pavel@....cz>:
> Hi!
>
>> So the /Documentation/timers/timers-howto.txt stats:
>>
>> SLEEPING FOR ~USECS OR SMALL MSECS ( 10us - 20ms):
>> * Use usleep_range
>>
>> - 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.
> ...
>> Should the documentation should be ignored?
>
> Caller wants to sleep for 10ms; docs said it may sleep for 10-20msec;
> that sounds reasonable. You replaced it with busy-loop for 10-15msec.
>
> That does not sound like improvement.
>
> Thanks,
>                                                                 Pavel
>
> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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