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Subject[PATCH 09/10] tick/nohz: Call tick_nohz_task_switch() with interrupts disabled
Date
From: Peter Zijlstra <peterz@infradead.org>

Call tick_nohz_task_switch() slightly earlier after the context switch
to benefit from disabled IRQs. This way the function doesn't need to
disable them once more.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Yunfeng Ye <yeyunfeng@huawei.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
kernel/sched/core.c | 2 +-
kernel/time/tick-sched.c | 7 +------
2 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 78e480f7881a..8f86ac28877e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4212,6 +4212,7 @@ static struct rq *finish_task_switch(struct task_struct *prev)
vtime_task_switch(prev);
perf_event_task_sched_in(prev, current);
finish_task(prev);
+ tick_nohz_task_switch();
finish_lock_switch(rq);
finish_arch_post_lock_switch();
kcov_finish_switch(current);
@@ -4257,7 +4258,6 @@ static struct rq *finish_task_switch(struct task_struct *prev)
put_task_struct_rcu_user(prev);
}

- tick_nohz_task_switch();
return rq;
}

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index d370a04deaa8..b748a71d8040 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -487,13 +487,10 @@ void tick_nohz_dep_clear_signal(struct signal_struct *sig, enum tick_dep_bits bi
*/
void __tick_nohz_task_switch(void)
{
- unsigned long flags;
struct tick_sched *ts;

- local_irq_save(flags);
-
if (!tick_nohz_full_cpu(smp_processor_id()))
- goto out;
+ return;

ts = this_cpu_ptr(&tick_cpu_sched);

@@ -502,8 +499,6 @@ void __tick_nohz_task_switch(void)
atomic_read(&current->signal->tick_dep_mask))
tick_nohz_full_kick();
}
-out:
- local_irq_restore(flags);
}

/* Get the boot-time nohz CPU list from the kernel parameters. */
--
2.25.1
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