From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <frederic@kernel.org>,
Yunfeng Ye <yeyunfeng@huawei.com>
Subject: [patch 6/7] tick/sched: Release seqcount before invoking calc_load_global()
Date: Tue, 17 Nov 2020 14:19:48 +0100 [thread overview]
Message-ID: <20201117132006.660902274@linutronix.de> (raw)
In-Reply-To: 20201117131942.515430545@linutronix.de
calc_load_global() does not need the sequence count protection.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/time/tick-sched.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -20,6 +20,7 @@
#include <linux/sched/clock.h>
#include <linux/sched/stat.h>
#include <linux/sched/nohz.h>
+#include <linux/sched/loadavg.h>
#include <linux/module.h>
#include <linux/irq_work.h>
#include <linux/posix-timers.h>
@@ -107,7 +108,8 @@ static void tick_do_update_jiffies64(kti
tick_period);
}
- do_timer(ticks);
+ /* Advance jiffies to complete the jiffies_seq protected job */
+ jiffies_64 += ticks;
/*
* Keep the tick_next_period variable up to date. WRITE_ONCE()
@@ -116,7 +118,15 @@ static void tick_do_update_jiffies64(kti
WRITE_ONCE(tick_next_period,
ktime_add(last_jiffies_update, tick_period));
+ /*
+ * Release the sequence count. calc_global_load() below is not
+ * protected by it, but jiffies_lock needs to be held to prevent
+ * concurrent invocations.
+ */
write_seqcount_end(&jiffies_seq);
+
+ calc_global_load();
+
raw_spin_unlock(&jiffies_lock);
update_wall_time();
}
next prev parent reply other threads:[~2020-11-17 14:24 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-17 13:19 [patch 0/7] tick: Cleanups and reduce jiffies_seq held times Thomas Gleixner
2020-11-17 13:19 ` [patch 1/7] tick/broadcast: Serialize access to tick_next_period Thomas Gleixner
2020-11-19 9:55 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2020-11-17 13:19 ` [patch 2/7] tick: Document protections for tick related data Thomas Gleixner
2020-11-19 9:55 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2020-11-17 13:19 ` [patch 3/7] tick/sched: Use tick_next_period for lockless quick check Thomas Gleixner
2020-11-19 9:55 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2020-11-17 13:19 ` [patch 4/7] tick/sched: Reduce seqcount held scope in tick_do_update_jiffies64() Thomas Gleixner
2020-11-19 9:55 ` [tip: timers/core] " tip-bot2 for Yunfeng Ye
2020-11-17 13:19 ` [patch 5/7] tick/sched: Optimize tick_do_update_jiffies64() further Thomas Gleixner
2020-11-19 9:55 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2020-11-17 13:19 ` Thomas Gleixner [this message]
2020-11-19 9:55 ` [tip: timers/core] tick/sched: Release seqcount before invoking calc_load_global() tip-bot2 for Yunfeng Ye
2020-11-17 13:19 ` [patch 7/7] tick: Get rid of tick_period Thomas Gleixner
2020-11-19 9:55 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
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