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Commit 9014c45d authored by Frederic Weisbecker's avatar Frederic Weisbecker
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nohz: Implement full dynticks kick 



Implement the full dynticks kick that is performed from
IPIs sent by various subsystems (scheduler, posix timers, ...)
when they want to notify about a new event that may
reconsider the dependency on the tick.

Most of the time, such an event end up restarting the tick.

(Part of the design with subsystems providing *_can_stop_tick()
helpers suggested by Peter Zijlstra a while ago).

Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
parent ff442c51

kernel/time/tick-sched.c

+38 −4
Original line number Diff line number Diff line
@@ -21,6 +21,8 @@ 
#include <linux/sched.h>

#include <linux/module.h>

#include <linux/irq_work.h>

#include <linux/posix-timers.h>

#include <linux/perf_event.h>



#include <asm/irq_regs.h>
@@ -147,16 +149,48 @@ static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs) 
static cpumask_var_t nohz_full_mask;

bool have_nohz_full_mask;



static bool can_stop_full_tick(void)

{

	WARN_ON_ONCE(!irqs_disabled());



	if (!sched_can_stop_tick())

		return false;



	if (!posix_cpu_timers_can_stop_tick(current))

		return false;



	if (!perf_event_can_stop_tick())

		return false;



	/* sched_clock_tick() needs us? */

#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK

	/*

	 * TODO: kick full dynticks CPUs when

	 * sched_clock_stable is set.

	 */

	if (!sched_clock_stable)

		return false;

#endif



	return true;

}



static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now);



/*

 * Re-evaluate the need for the tick on the current CPU

 * and restart it if necessary.

 */

void tick_nohz_full_check(void)

{

	/*

	 * STUB for now, will be filled with the full tick stop/restart

	 * infrastructure patches

	 */

	struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);



	if (tick_nohz_full_cpu(smp_processor_id())) {

		if (ts->tick_stopped && !is_idle_task(current)) {

			if (!can_stop_full_tick())

				tick_nohz_restart_sched_tick(ts, ktime_get());

		}

	}

}



static void nohz_full_kick_work_func(struct irq_work *work)