tick/sched: Release seqcount before invoking calc_load_global()

calc_load_global() does not need the sequence count protection.

[ tglx: Split it up properly and added comments ]

Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201117132006.660902274@linutronix.de

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 306adeb6ce4c4abfc0f92b5ee3e06359bd490d81..33c897bb88c6ef419b08bf18f9e7507760451dbb 100644 (file)
--- 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(ktime_t now)
                                                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(ktime_t now)
        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();
 }