linux-kernel - Re: [PATCH v3 1/2] perf, x86: Implement event scheduler helper functions

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Message-ID: <1321459336.27735.8.camel@twins>
Date:	Wed, 16 Nov 2011 17:02:16 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Robert Richter <robert.richter@....com>
Cc:	Stephane Eranian <eranian@...gle.com>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/2] perf, x86: Implement event scheduler helper
 functions

On Mon, 2011-11-14 at 18:51 +0100, Robert Richter wrote:
> @@ -22,8 +22,14 @@ extern unsigned long __sw_hweight64(__u64 w);
>  #include <asm/bitops.h>
>  
>  #define for_each_set_bit(bit, addr, size) \
> -       for ((bit) = find_first_bit((addr), (size)); \
> -            (bit) < (size); \
> +       for ((bit) = find_first_bit((addr), (size));            \
> +            (bit) < (size);                                    \
> +            (bit) = find_next_bit((addr), (size), (bit) + 1))
> +
> +/* same as for_each_set_bit() but use bit as value to start with */
> +#define for_each_set_bit_cont(bit, addr, size) \
> +       for ((bit) = find_next_bit((addr), (size), (bit));      \
> +            (bit) < (size);                                    \
>              (bit) = find_next_bit((addr), (size), (bit) + 1)) 

So my version has the +1 for the first as well, this is from the
assumption that the bit passed in has been dealt with and should not be
the first. ie. cont _after_ @bit instead of cont _at_ @bit.

This seems consistent with the list_*_continue primitives as well, which
will start with the element after (or before for _reverse) the given
position.

Thoughts?
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