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authorFrederic Weisbecker <fweisbec@gmail.com>2013-04-20 17:11:50 +0200
committerFrederic Weisbecker <fweisbec@gmail.com>2013-04-22 20:29:07 +0200
commit99e5ada9407cc19d7c4c05ce2165f20dc46fc093 (patch)
tree6d39bf6095e18b82f78b3cc405d49fbb8836b299 /kernel
parent5811d9963e26146898a24b535b301f7654257f8a (diff)
downloadlinaro-lsk-99e5ada9407cc19d7c4c05ce2165f20dc46fc093.tar.gz
nohz: Re-evaluate the tick for the new task after a context switch
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 <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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched/core.c2
-rw-r--r--kernel/time/tick-sched.c20
2 files changed, 22 insertions, 0 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9ad35005f1c..dd09def8856 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 d0ed1905a85..12a900dbb81 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)