lkml.org 
[lkml]   [2014]   [Mar]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH V2 2/2] hrtimer: use __ffs() to iterate over valid bits from active_bases
    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


    \
     
     \ /
      Last update: 2014-03-27 07:21    [W:3.976 / U:0.420 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site