From: Frederic Weisbecker <frederic@kernel.org> 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=... -------------------------------- commit 3e61e95e2d095e308616cba4ffb640f95a480e01 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: Valentin Schneider <valentin.schneider@arm.com> Tested-by: Valentin Schneider <valentin.schneider@arm.com> Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Frederic 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: Paul E. McKenney <paulmck@kernel.org> [UR: backport to 5.10-stable + commit update] Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> Acked-by: Xie XiuQi <xiexiuqi@huawei.com> --- kernel/rcu/tree.c | 28 ++++++++++++++++------------ 1 file changed, 16 insertions(+), 12 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 310bcc79b07b..4d4d93fb94fc 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -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() || - (!is_idle_task(current) && !rcu_is_callbacks_kthread()))) - break; + 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); -- 2.20.1