linux-kernel - [PATCH 09/10] tick/nohz: Call tick_nohz_task

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Message-Id: <20210512232924.150322-10-frederic@kernel.org>
Date:   Thu, 13 May 2021 01:29:23 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Yunfeng Ye <yeyunfeng@...wei.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Marcelo Tosatti <mtosatti@...hat.com>
Subject: [PATCH 09/10] tick/nohz: Call tick_nohz_task_switch() with interrupts disabled

From: Peter Zijlstra <peterz@...radead.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@...radead.org>
Cc: Marcelo Tosatti <mtosatti@...hat.com>
Cc: Yunfeng Ye <yeyunfeng@...wei.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Frederic Weisbecker <frederic@...nel.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