On 2 April 2015 at 19:15, Peter Zijlstra <pet...@infradead.org> wrote:
> 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.
Okay what about this instead (This is the best I could write :).) ?
+static inline int __next_bit(unsigned int active_bases, int bit)
+{
+ do {
+ if (active_bases & (1 << bit))
+ return bit;
+ } while (++bit < HRTIMER_MAX_CLOCK_BASES);
+
+ /* We should never reach here */
+ return 0;
+}
+/*
+ * for_each_active_base: iterate over all active clock bases
+ * @_bit: 'int' variable for internal purpose
+ * @_base: holds pointer to a active clock base
+ * @_cpu_base: cpu base to iterate on
+ * @_active_bases: 'unsigned int' variable for internal purpose
+ */
+#define for_each_active_base(_bit, _base, _cpu_base, _active_bases) \
+ for ((_active_bases) = (_cpu_base)->active_bases, (_bit) = -1; \
+ (_active_bases) && \
+ ((_bit) = __next_bit(_active_bases, ++_bit), \
+ (_base) = (_cpu_base)->clock_base + _bit); \
+ (_active_bases) &= ~(1 << (_bit)))
+
Tested it well with the help of: http://pastebin.com/cYyB513D, with
inputs from 0 to 15.
I will send it formally if it looks fine to you ..
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