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From: Arnd Bergmann <arnd@arndb.de>
To: Andreas Schwab <schwab@linux-m68k.org>
Subject: Re: [PATCH] procfs: do not confuse jiffies with cputime64_t
Date: Mon, 12 Dec 2011 09:22:13 +0000
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On Monday 12 December 2011, Andreas Schwab wrote:
> @@ -46,7 +46,7 @@ static cputime64_t get_iowait_time(int cpu)
>                 /* !NO_HZ so we can rely on cpustat.iowait */
>                 iowait = kstat_cpu(cpu).cpustat.iowait;
>         else
> -               iowait = nsecs_to_jiffies64(1000 * iowait_time);
> +               iowait = jiffies64_to_cputime64(nsecs_to_jiffies64(1000 * iowait_time));
>  
>         return iowait;

Hmm, shouldn't this be using nsecs_to_cputime64()? For some reason however, that function
is (incorrectly?) defined as 

include/asm-generic/cputime.h:#define nsecs_to_cputime64(__ct)  nsecs_to_jiffies64(__ct)

and only used in one place, in

kernel/sched.c: if (cputime64_gt(nsecs_to_cputime64(latest_ns), cpustat->irq))
kernel/sched.c: if (cputime64_gt(nsecs_to_cputime64(latest_ns), cpustat->softirq))

I'm not sure what the correct solution is, but I would assume that ia64 and powerpc
should fix their definitions of nsecs_to_cputime64() anyway.

	Arnd