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Subject[PATCH 13/41] nohz/cpuset: Don't stop the tick if posix cpu timers are running
Date
If either a per thread or a per process posix cpu timer is running,
don't stop the tick.

TODO: restart the tick if it is stopped and a posix cpu timer is
enqueued. Check we probably need a memory barrier for the per
process posix timer that can be enqueued from another task
of the group.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
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@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
include/linux/posix-timers.h | 1 +
kernel/posix-cpu-timers.c | 12 ++++++++++++
kernel/time/tick-sched.c | 4 ++++
3 files changed, 17 insertions(+), 0 deletions(-)
diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index 042058f..97480c2 100644
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -119,6 +119,7 @@ int posix_timer_event(struct k_itimer *timr, int si_private);
void posix_cpu_timer_schedule(struct k_itimer *timer);

void run_posix_cpu_timers(struct task_struct *task);
+bool posix_cpu_timers_running(struct task_struct *tsk);
void posix_cpu_timers_exit(struct task_struct *task);
void posix_cpu_timers_exit_group(struct task_struct *task);

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 125cb67..79d4c24 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -6,6 +6,7 @@
#include <linux/posix-timers.h>
#include <linux/errno.h>
#include <linux/math64.h>
+#include <linux/cpuset.h>
#include <asm/uaccess.h>
#include <linux/kernel_stat.h>
#include <trace/events/timer.h>
@@ -1274,6 +1275,17 @@ static inline int fastpath_timer_check(struct task_struct *tsk)
return 0;
}

+bool posix_cpu_timers_running(struct task_struct *tsk)
+{
+ if (!task_cputime_zero(&tsk->cputime_expires))
+ return true;
+
+ if (tsk->signal->cputimer.running)
+ return true;
+
+ return false;
+}
+
/*
* This is called from the timer interrupt handler. The irq handler has
* already updated our counts. We need to check if any timers fire now.
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 4f99766..fc35d41 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -21,6 +21,7 @@
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/cpuset.h>
+#include <linux/posix-timers.h>

#include <asm/irq_regs.h>

@@ -512,6 +513,9 @@ static bool can_stop_adaptive_tick(void)
if (!sched_can_stop_tick())
return false;

+ if (posix_cpu_timers_running(current))
+ return false;
+
/* Is there a grace period to complete ? */
if (rcu_pending(smp_processor_id()))
return false;
--
1.7.5.4


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