linux-kernel - Re: [PATCH 2/2] hrtimer: create for_each_active_base() to iterate over active clock-bases

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Message-ID: <20150402134519.GA23123@twins.programming.kicks-ass.net>
Date:	Thu, 2 Apr 2015 15:45:19 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, linaro-kernel@...ts.linaro.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] hrtimer: create for_each_active_base() to iterate
 over active clock-bases

On Thu, Apr 02, 2015 at 04:21:22PM +0530, Viresh Kumar wrote:
> +#define for_each_active_base(_index, _base, _cpu_base, _active_bases)	\
> +	for ((_active_bases) = (_cpu_base)->active_bases;		\
> +		(_index) = ffs(_active_bases),				\
> +		(_base) = (_cpu_base)->clock_base + (_index) - 1, (_index); \
> +		(_active_bases) &= ~(1 << ((_index) - 1)))

Can't use ffs here, some people end up using asm-generic/bitops/ffs.h
and that sucks.

Esp for small vectors like here, the unconditional iteration is faster.
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