linux-kernel - Re: [PATCH] kernel.h: make abs() work with 64-bit types

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Message-ID: <CALAqxLVQv979j-y1RW0Xj2-MsHZjq=-5D0WcfsiZ+hsMc557Aw@mail.gmail.com>
Date:	Thu, 17 Sep 2015 20:12:23 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Michal Nazarewicz <mina86@...a86.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] kernel.h: make abs() work with 64-bit types

On Wed, Sep 16, 2015 at 5:57 AM, Michal Nazarewicz <mina86@...a86.com> wrote:
> For 64-bit arguments, abs macro casts it to an int which leads to lost
> precision and may cause incorrect results.  To deal with 64-bit types
> abs64 macro has been introduced but still there are places where abs
> macro is used incorrectly.
>
> To deal with the problem, expand abs macro such that it operates on s64
> type when dealing with 64-bit types while still returning long when
> dealing with smaller types.
>
> Signed-off-by: Michal Nazarewicz <mina86@...a86.com>

Sorry this is a little late, but I did run this patch through my tests
on a 32bit system (against 4.2, since my localized fix has already
landed in Linus' head) to make sure it resolved the bug I saw and it
did.

So,
Tested-by: John Stultz <john.stultz@...aro.org>

thanks!
-john
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