Messages in this thread | | | Date | Thu, 27 Mar 2014 06:40:58 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH V2 2/2] hrtimer: use __ffs() to iterate over valid bits from active_bases |
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On Thu, 27 Mar 2014, Viresh Kumar wrote:
> Currently we are iterating over all possible (currently four) bits of > active_bases to see if corresponding clock bases are active. This is good enough > for cases where 3 or 4 bases are used but if only 1 or 2 are used then it makes > more sense to use __ffs() to find the right bit directly. > > Suggested-by: Thomas Gleixner <tglx@linutronix.de> > Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> > --- > V1->V2: Instead of removing active_bases use __ffs() on it to make loop more > efficient. > > I tried to use for_each_set_bit() first and then it looked overdone. And so used > a simple form, __ffs() with some code to clear bits. > > kernel/hrtimer.c | 11 +++++------ > 1 file changed, 5 insertions(+), 6 deletions(-) > > diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c > index acfef5f..ea90228 100644 > --- a/kernel/hrtimer.c > +++ b/kernel/hrtimer.c > @@ -1265,6 +1265,7 @@ void hrtimer_interrupt(struct clock_event_device *dev) > { > struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases); > ktime_t expires_next, now, entry_time, delta; > + unsigned long active_bases = cpu_base->active_bases; > int i, retries = 0; > > BUG_ON(!cpu_base->hres_active); > @@ -1284,15 +1285,11 @@ retry: > */ > cpu_base->expires_next.tv64 = KTIME_MAX; > > - for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) { > - struct hrtimer_clock_base *base; > + while ((i = __ffs(active_bases))) {
What if this is a spurious interrupt and active_bases is 0?
Thanks,
tglx
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