| Message ID | aa0ab84ff46cdc4a2d7aef475b2c032009f23d29.1395897612.git.viresh.kumar@linaro.org |
|---|---|
| State | New |
| Headers | show |
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 -- 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/
On 27 March 2014 11:10, Thomas Gleixner <tglx@linutronix.de> wrote:
> What if this is a spurious interrupt and active_bases is 0?
Hmm.. haven't thought about that actually.. I thought it would be
guaranteed here that active_bases isn't zero.
Will fix it as the current code would end up in a infinite loop.
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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))) { + struct hrtimer_clock_base *base = cpu_base->clock_base + i; struct timerqueue_node *node; ktime_t basenow; - if (!(cpu_base->active_bases & (1 << i))) - continue; - - base = cpu_base->clock_base + i; basenow = ktime_add(now, base->offset); while ((node = timerqueue_getnext(&base->active))) { @@ -1327,6 +1324,8 @@ retry: __run_hrtimer(timer, &basenow); } + + active_bases &= ~(1 << i); } /*
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(-)