tick/sched: Reduce seqcount held scope in tick_do_update_jiffies64() (94ad2e3c) · Commits · 戴 / test

kernel/time/tick-sched.c

+22 −25

Original line number	Diff line number	Diff line
		@@ -86,17 +86,18 @@ static void tick_do_update_jiffies64(ktime_t now)

		/* Reevaluate with jiffies_lock held */
		raw_spin_lock(&jiffies_lock);
		write_seqcount_begin(&jiffies_seq);
		if (ktime_before(now, tick_next_period)) {
		raw_spin_unlock(&jiffies_lock);
		return;
		}

		delta = ktime_sub(now, last_jiffies_update);
		if (delta >= tick_period) {
		write_seqcount_begin(&jiffies_seq);

		delta = ktime_sub(delta, tick_period);
		last_jiffies_update = ktime_add(last_jiffies_update,
		tick_period);
		last_jiffies_update = ktime_add(last_jiffies_update, tick_period);

		/* Slow path for long timeouts */
		delta = ktime_sub(now, tick_next_period);
		if (unlikely(delta >= tick_period)) {
		/* Slow path for long idle sleep times */
		s64 incr = ktime_to_ns(tick_period);

		ticks = ktime_divns(delta, incr);
		@@ -104,20 +105,16 @@ static void tick_do_update_jiffies64(ktime_t now)
		last_jiffies_update = ktime_add_ns(last_jiffies_update,
		incr * ticks);
		}

		do_timer(++ticks);

		/*
		* Keep the tick_next_period variable up to date.
		* WRITE_ONCE() pairs with the READ_ONCE() in the lockless
		* quick check above.
		* Keep the tick_next_period variable up to date. WRITE_ONCE()
		* pairs with the READ_ONCE() in the lockless quick check above.
		*/
		WRITE_ONCE(tick_next_period,
		ktime_add(last_jiffies_update, tick_period));
		} else {
		write_seqcount_end(&jiffies_seq);
		raw_spin_unlock(&jiffies_lock);
		return;
		}

		write_seqcount_end(&jiffies_seq);
		raw_spin_unlock(&jiffies_lock);
		update_wall_time();