Commit 8daec20c authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Zheng Zengkai
Browse files

rcu: Fix callbacks processing time limit retaining cond_resched() 

stable inclusion
from stable-v5.10.115
commit 40fb3812d99746f0322ada92fdc8d904a024e6de
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5IZ9C

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=40fb3812d99746f0322ada92fdc8d904a024e6de



--------------------------------

commit 3e61e95e upstream.

The callbacks processing time limit makes sure we are not exceeding a
given amount of time executing the queue.

However its "continue" clause bypasses the cond_resched() call on
rcuc and NOCB kthreads, delaying it until we reach the limit, which can
be very long...

Make sure the scheduler has a higher priority than the time limit.

Reviewed-by: default avatarValentin Schneider <valentin.schneider@arm.com>
Tested-by: default avatarValentin Schneider <valentin.schneider@arm.com>
Tested-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
[UR: backport to 5.10-stable + commit update]
Signed-off-by: default avatarUladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: default avatarXie XiuQi <xiexiuqi@huawei.com>
parent dab6aad5

kernel/rcu/tree.c

+16 −12
Original line number Diff line number Diff line
@@ -2512,10 +2512,22 @@ static void rcu_do_batch(struct rcu_data *rdp) 
		 * Stop only if limit reached and CPU has something to do.

		 * Note: The rcl structure counts down from zero.

		 */

		if (-rcl.len >= bl && !offloaded &&

		    (need_resched() ||

		if (in_serving_softirq()) {

			if (-rcl.len >= bl && (need_resched() ||

					(!is_idle_task(current) && !rcu_is_callbacks_kthread())))

				break;

		} else {

			local_bh_enable();

			lockdep_assert_irqs_enabled();

			cond_resched_tasks_rcu_qs();

			lockdep_assert_irqs_enabled();

			local_bh_disable();

		}



		/*

		 * Make sure we don't spend too much time here and deprive other

		 * softirq vectors of CPU cycles.

		 */

		if (unlikely(tlimit)) {

			/* only call local_clock() every 32 callbacks */

			if (likely((-rcl.len & 31) || local_clock() < tlimit))
@@ -2523,14 +2535,6 @@ static void rcu_do_batch(struct rcu_data *rdp) 
			/* Exceeded the time limit, so leave. */

			break;

		}

		if (offloaded) {

			WARN_ON_ONCE(in_serving_softirq());

			local_bh_enable();

			lockdep_assert_irqs_enabled();

			cond_resched_tasks_rcu_qs();

			lockdep_assert_irqs_enabled();

			local_bh_disable();

		}

	}



	local_irq_save(flags);