On 03/05/2013 09:40 PM, Thomas Gleixner wrote: > On Sat, 2 Mar 2013, Daniel Lezcano wrote: >> When a cpu goes to a deep idle state where its local timer is shutdown, >> it notifies the time frame work to use the broadcast timer instead. >> >> Unfortunately, the broadcast device could wake up any CPU, including an >> idle one which is not concerned by the wake up at all. >> >> This implies, in the worst case, an idle CPU will wake up to send an IPI >> to another idle cpu. >> >> This patch solves this by setting the irq affinity to the cpu concerned >> by the nearest timer event, by this way, the CPU which is wake up is >> guarantee to be the one concerned by the next event and we are safe with >> unnecessary wakeup for another idle CPU. >> >> As the irq affinity is not supported by all the archs, a flag is needed >> to specify which clocksource can handle it : CLOCK_EVT_FEAT_DYNIRQ >> >> Signed-off-by: Daniel Lezcano <daniel.lezc...@linaro.org> >> --- >> include/linux/clockchips.h | 5 +++++ >> kernel/time/tick-broadcast.c | 40 +++++++++++++++++++++++++++++++++------- >> 2 files changed, 38 insertions(+), 7 deletions(-) >> >> diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h >> index 6634652..c93e2a6 100644 >> --- a/include/linux/clockchips.h >> +++ b/include/linux/clockchips.h >> @@ -55,6 +55,11 @@ enum clock_event_nofitiers { >> #define CLOCK_EVT_FEAT_C3STOP 0x000008 >> #define CLOCK_EVT_FEAT_DUMMY 0x000010 >> >> +/* >> + * Clock event device can set its irq affinity dynamically >> + */ >> +#define CLOCK_EVT_FEAT_DYNIRQ 0x000020 >> + >> /** >> * struct clock_event_device - clock event device descriptor >> * @event_handler: Assigned by the framework to be called by the low >> diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c >> index 6197ac0..9ca8ff5 100644 >> --- a/kernel/time/tick-broadcast.c >> +++ b/kernel/time/tick-broadcast.c >> @@ -406,13 +406,37 @@ struct cpumask *tick_get_broadcast_oneshot_mask(void) >> return to_cpumask(tick_broadcast_oneshot_mask); >> } >> >> -static int tick_broadcast_set_event(struct clock_event_device *bc, >> +/* >> + * Set broadcast interrupt affinity >> + */ >> +static void tick_broadcast_set_affinity(struct clock_event_device *bc, >> + const struct cpumask *cpumask) >> +{ >> + if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ)) >> + return; >> + >> + if (cpumask_equal(bc->cpumask, cpumask)) >> + return; >> + >> + bc->cpumask = cpumask; > > This breaks with CONFIG_CPUMASK_OFFSTACK=y. cpumask_copy() is your friend!
This instruction copies the pointer, not the cpumask content. bc->cpumask is defined as a const struct cpumask * and is used to copy a cpumask pointer not the content. The cpumask parameter is a pointer to a global cpumask provided by the cpumask_of macro. But to be in the safe side, I compiled tested with CONFIG_CPUMASK_OFFSTACK=y without problem. Did I missed something ? Thanks -- Daniel > -- > To unsubscribe from this list: send the line "unsubscribe linux-pm" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/