When a task is scheduled in, it may have some properties of its own that could make the CPU reconsider the need for the tick: posix cpu timers, perf events, ...
So notify the full dynticks subsystem when a task gets scheduled in and re-check the tick dependency at this stage. This is done through a self IPI to avoid messing up with any current lock scenario. Signed-off-by: Frederic Weisbecker <[email protected]> Cc: Chris Metcalf <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: Geoff Levand <[email protected]> Cc: Gilad Ben Yossef <[email protected]> Cc: Hakan Akkan <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Kevin Hilman <[email protected]> Cc: Li Zhong <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Paul E. McKenney <[email protected]> Cc: Paul Gortmaker <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: Thomas Gleixner <[email protected]> --- include/linux/tick.h | 2 ++ kernel/sched/core.c | 2 ++ kernel/time/tick-sched.c | 20 ++++++++++++++++++++ 3 files changed, 24 insertions(+), 0 deletions(-) diff --git a/include/linux/tick.h b/include/linux/tick.h index e31e676..9180f4b 100644 --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -163,12 +163,14 @@ extern int tick_nohz_full_cpu(int cpu); extern void tick_nohz_full_check(void); extern void tick_nohz_full_kick(void); extern void tick_nohz_full_kick_all(void); +extern void tick_nohz_task_switch(struct task_struct *tsk); #else static inline void tick_nohz_init(void) { } static inline int tick_nohz_full_cpu(int cpu) { return 0; } static inline void tick_nohz_full_check(void) { } static inline void tick_nohz_full_kick(void) { } static inline void tick_nohz_full_kick_all(void) { } +static inline void tick_nohz_task_switch(struct task_struct *tsk) { } #endif diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 9ad3500..dd09def 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1896,6 +1896,8 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev) kprobe_flush_task(prev); put_task_struct(prev); } + + tick_nohz_task_switch(current); } #ifdef CONFIG_SMP diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index d0ed190..12a900d 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -232,6 +232,26 @@ void tick_nohz_full_kick_all(void) preempt_enable(); } +/* + * Re-evaluate the need for the tick as we switch the current task. + * It might need the tick due to per task/process properties: + * perf events, posix cpu timers, ... + */ +void tick_nohz_task_switch(struct task_struct *tsk) +{ + unsigned long flags; + + if (!tick_nohz_full_cpu(smp_processor_id())) + return; + + local_irq_save(flags); + + if (tick_nohz_tick_stopped() && !can_stop_full_tick()) + tick_nohz_full_kick(); + + local_irq_restore(flags); +} + int tick_nohz_full_cpu(int cpu) { if (!have_nohz_full_mask) -- 1.7.5.4 -- 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/
