This allows other parts of the kernel access to the tick_do_timer_cpu variable in a controlled manner. The values will differ depending on which mode is compiled in:
* CONFIG_HZ_PERIODIC: One (normally boot-cpu) is responsible for the time update. This will never change unless the CPU is removed (hotplugging). You will normally see a 0 returned every time here. * CONFIG_NO_HZ_IDLE: system will disable periodic timer-interrupts on the cpu if only the idle-task is running. This means that the timer cpu will change often. * CONFIG_NO_HZ_FULL: any CPU running only a single task can have timer-interrupts disabled. As for NO_HZ_IDLE, timer CPU will change often. CC: Thomas Gleixner <[email protected]> CC: Peter Zijlstra <[email protected]> CC: Frederic Weisbecker <[email protected]> CC: John Stultz <[email protected]> Signed-off-by: Henrik Austad <[email protected]> --- kernel/time/tick-common.c | 12 ++++++++++++ kernel/time/tick-internal.h | 1 + 2 files changed, 13 insertions(+) diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c index 20b2fe3..1729b4b 100644 --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -348,6 +348,18 @@ void tick_handover_do_timer(int *cpup) } /* + * Return the current timer-CPU (RO) + * + * Warning! this value can (and will) change depending on how timer-ticks are + * handled, the value returned could be outdated the moment it is read by + * userspace. + */ +int tick_expose_cpu(void) +{ + return tick_do_timer_cpu; +} + +/* * Shutdown an event device on a given cpu: * * This is called on a life CPU, when a CPU is dead. So we cannot diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h index 8329669..5051dbd 100644 --- a/kernel/time/tick-internal.h +++ b/kernel/time/tick-internal.h @@ -154,5 +154,6 @@ static inline int tick_device_is_functional(struct clock_event_device *dev) #endif +extern int tick_expose_cpu(void); extern void do_timer(unsigned long ticks); extern void update_wall_time(void); -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
