Commit 5811d996 authored Apr 20, 2013 by Frederic Weisbecker

nohz: Prepare to stop the tick on irq exit



Interrupt exit is a natural place to stop the tick: it happens
after all events happening before and during the irq which
are liable to update the dependency on the tick occured. Also
it makes sure that any check on tick dependency is well ordered
against dynticks kick IPIs.

Bring in the infrastructure that performs the tick dependency
checks on irq exit and shut it down if these checks show that we
can do it safely.

Signed-off-by: Frederic 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 9014c45d

kernel/time/tick-sched.c

+25 −6

Original line number	Diff line number	Diff line
		@@ -647,6 +647,24 @@ out:
		return ret;
		}

		static void tick_nohz_full_stop_tick(struct tick_sched *ts)
		{
		#ifdef CONFIG_NO_HZ_FULL
		int cpu = smp_processor_id();

		if (!tick_nohz_full_cpu(cpu) \|\| is_idle_task(current))
		return;

		if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
		return;

		if (!can_stop_full_tick())
		return;

		tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
		#endif
		}

		static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
		{
		/*
		@@ -773,12 +791,13 @@ void tick_nohz_irq_exit(void)
		{
		struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);

		if (!ts->inidle)
		return;

		if (ts->inidle) {
		/* Cancel the timer because CPU already waken up from the C-states*/
		menu_hrtimer_cancel();
		__tick_nohz_idle_enter(ts);
		} else {
		tick_nohz_full_stop_tick(ts);
		}
		}

		/**

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