lkml.org 
[lkml]   [2012]   [Mar]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [RFC PATCH 5/6] implement per-cpu&per-domain state machine call_srcu()
From
On Tue, Mar 6, 2012 at 6:58 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Tue, 2012-03-06 at 17:57 +0800, Lai Jiangshan wrote:
>>  /*
>> + * 'return left < right;' but handle the overflow issues.
>> + * The same as 'return (long)(right - left) > 0;' but it cares more.
>
> About what? And why? We do the (long)(a - b) thing all over the kernel,
> why would you care more?

@left is constants of the callers(callbacks's snapshot), @right
increases very slow.
if (long)(right - left) is a big negative, we have to wait for a long
time in this kinds of overflow.
this kinds of overflow can not happen in this safe_less_than()

>
>> + */
>> +static inline
>> +bool safe_less_than(unsigned long left, unsigned long right, unsigned long max)
>> +{
>> +       unsigned long a = right - left;
>> +       unsigned long b = max - left;
>> +
>> +       return !!a && (a <= b);
>> +}
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2012-03-06 16:19    [W:0.191 / U:4.024 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site