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rcu: Fix callbacks processing time limit retaining cond_resched()
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>
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1 changed files with 15 additions and 10 deletions
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@ -2525,9 +2525,21 @@ static void rcu_do_batch(struct rcu_data *rdp)
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/*
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* Stop only if limit reached and CPU has something to do.
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*/
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if (count >= bl && in_serving_softirq() &&
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(need_resched() || !is_idle_task(current)))
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break;
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if (in_serving_softirq()) {
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if (count >= bl && (need_resched() || !is_idle_task(current)))
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break;
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} else {
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local_bh_enable();
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lockdep_assert_irqs_enabled();
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cond_resched_tasks_rcu_qs();
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lockdep_assert_irqs_enabled();
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local_bh_disable();
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}
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/*
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* Make sure we don't spend too much time here and deprive other
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* softirq vectors of CPU cycles.
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*/
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if (unlikely(tlimit)) {
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/* only call local_clock() every 32 callbacks */
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if (likely((count & 31) || local_clock() < tlimit))
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@ -2535,13 +2547,6 @@ static void rcu_do_batch(struct rcu_data *rdp)
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/* Exceeded the time limit, so leave. */
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break;
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}
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if (!in_serving_softirq()) {
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local_bh_enable();
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lockdep_assert_irqs_enabled();
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cond_resched_tasks_rcu_qs();
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lockdep_assert_irqs_enabled();
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local_bh_disable();
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}
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}
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rcu_nocb_lock_irqsave(rdp, flags);
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