Commit-ID: 22ab8bc02a5f6e8ffc418759894f7a6b0b632331
Gitweb: https://git.kernel.org/tip/22ab8bc02a5f6e8ffc418759894f7a6b0b632331
Author: Frederic Weisbecker <frederic@xxxxxxxxxx>
AuthorDate: Wed, 21 Feb 2018 05:17:25 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 21 Feb 2018 09:49:08 +0100
nohz: Allow to check if remote CPU tick is stopped
This check is racy but provides a good heuristic to determine whether
a CPU may need a remote tick or not.
Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Chris Metcalf <cmetcalf@xxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Luiz Capitulino <lcapitulino@xxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Wanpeng Li <kernellwp@xxxxxxxxx>
Link: http://lkml.kernel.org/r/1519186649-3242-4-git-send-email-frederic@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
include/linux/tick.h | 2 ++
kernel/time/tick-sched.c | 7 +++++++
2 files changed, 9 insertions(+)
diff --git a/include/linux/tick.h b/include/linux/tick.h
index 86576d9..7f8c9a1 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -114,6 +114,7 @@ enum tick_dep_bits {
#ifdef CONFIG_NO_HZ_COMMON
extern bool tick_nohz_enabled;
extern bool tick_nohz_tick_stopped(void);
+extern bool tick_nohz_tick_stopped_cpu(int cpu);
extern void tick_nohz_idle_enter(void);
extern void tick_nohz_idle_exit(void);
extern void tick_nohz_irq_exit(void);
@@ -125,6 +126,7 @@ extern u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time);
#else /* !CONFIG_NO_HZ_COMMON */
#define tick_nohz_enabled (0)
static inline int tick_nohz_tick_stopped(void) { return 0; }
+static inline int tick_nohz_tick_stopped_cpu(int cpu) { return 0; }
static inline void tick_nohz_idle_enter(void) { }
static inline void tick_nohz_idle_exit(void) { }
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 0aba041..d479b21 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -486,6 +486,13 @@ bool tick_nohz_tick_stopped(void)
return __this_cpu_read(tick_cpu_sched.tick_stopped);
}
+bool tick_nohz_tick_stopped_cpu(int cpu)
+{
+ struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu);
+
+ return ts->tick_stopped;
+}
+
/**
* tick_nohz_update_jiffies - update jiffies when idle was interrupted
*
--
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