linux-kernel - Re: [resend PATCH for 3.2] procfs: do not confuse jiffies with cputime64

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Message-ID: <m2zkelo428.fsf@igel.home>
Date:	Thu, 22 Dec 2011 01:14:39 +0100
From:	Andreas Schwab <schwab@...ux-m68k.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Michal Hocko <mhocko@...e.cz>, Arnd Bergmann <arnd@...db.de>,
	linux-kernel@...r.kernel.org,
	"Artem S. Tashkinov" <t.artem@...lcity.com>,
	Dave Jones <davej@...hat.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [resend PATCH for 3.2] procfs: do not confuse jiffies with cputime64_t

Andrew Morton <akpm@...ux-foundation.org> writes:

> On Thu, 22 Dec 2011 00:50:06 +0100
> Andreas Schwab <schwab@...ux-m68k.org> wrote:
>
>> Andrew Morton <akpm@...ux-foundation.org> writes:
>> 
>> > From: Andreas Schwab <schwab@...ux-m68k.org>
>> > Subject: procfs: do not confuse jiffies with cputime64_t
>> >
>> > get_{idle,iowait}_time are supposed to return cputime64_t values, not
>> > jiffies.  Add usecs_to_cputime64 for this.
>> 
>> For most architectures (which use the asm-generic/cputime.h) jiffies use
>> the same unit as cputime64_t values, but ia64, powerpc and s390 make
>> them different.
>> 
>
> OK, but
>
> a) what effect does this problem have upon users of the kernel?

get_idle_time returns the value in the wrong unit.

> b) which kernel version(s) are affected?

get_idle_time got broken in 2a95ea6c0d129b4568fb64e1deda16ceb20e6636.

$ git tag --contains a25cac5198d4ff2842ccca63b423962848ad24b2
v3.2-rc1
v3.2-rc2
v3.2-rc3
v3.2-rc4
v3.2-rc5
v3.2-rc6

Andreas.

-- 
Andreas Schwab, schwab@...ux-m68k.org
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