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nohz: Wake up full dynticks CPUs when a timer gets enqueued

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Wake up a CPU when a timer list timer is enqueued there and
the target is part of the full dynticks range. Sending an IPI
to it makes it reconsidering the next timer to program on top
of recent updates.

This may later be improved by checking if the tick is really
stopped on the target. This would need some careful
synchronization though. So deal with such optimization later
and start simple.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
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: Namhyung Kim <namhyung.kim@lge.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>
This commit is contained in:
Frederic Weisbecker 2011-08-10 23:21:01 +02:00
parent a382bf9344
commit 1c20091e77
3 changed files with 27 additions and 9 deletions
Download patch file Download diff file Expand all files Collapse all files

12
kernel/timer.c
View file

@ -930,14 +930,14 @@ void add_timer_on(struct timer_list *timer, int cpu)
debug_activate(timer, timer->expires);
internal_add_timer(base, timer);
/*
* Check whether the other CPU is idle and needs to be
* triggered to reevaluate the timer wheel when nohz is
* active. We are protected against the other CPU fiddling
* Check whether the other CPU is in dynticks mode and needs
* to be triggered to reevaluate the timer wheel.
* We are protected against the other CPU fiddling
* with the timer by holding the timer base lock. This also
* makes sure that a CPU on the way to idle can not evaluate
* the timer wheel.
* makes sure that a CPU on the way to stop its tick can not
* evaluate the timer wheel.
*/
wake_up_idle_cpu(cpu);
wake_up_nohz_cpu(cpu);
spin_unlock_irqrestore(&base->lock, flags);
}
EXPORT_SYMBOL_GPL(add_timer_on);