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rcu: Apply callbacks processing time limit only on softirq
Time limit only makes sense when callbacks are serviced in softirq mode because: _ In case we need to get back to the scheduler, cond_resched_tasks_rcu_qs() is called after each callback. _ In case some other softirq vector needs the CPU, the call to local_bh_enable() before cond_resched_tasks_rcu_qs() takes care about them via a call to do_softirq(). Therefore, make sure the time limit only applies to softirq mode. 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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parent
3e61e95e2d
commit
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1 changed files with 12 additions and 13 deletions
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@ -2488,7 +2488,7 @@ static void rcu_do_batch(struct rcu_data *rdp)
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div = READ_ONCE(rcu_divisor);
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div = div < 0 ? 7 : div > sizeof(long) * 8 - 2 ? sizeof(long) * 8 - 2 : div;
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bl = max(rdp->blimit, pending >> div);
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if (unlikely(bl > 100)) {
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if (in_serving_softirq() && unlikely(bl > 100)) {
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long rrn = READ_ONCE(rcu_resched_ns);
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rrn = rrn < NSEC_PER_MSEC ? NSEC_PER_MSEC : rrn > NSEC_PER_SEC ? NSEC_PER_SEC : rrn;
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@ -2528,6 +2528,17 @@ static void rcu_do_batch(struct rcu_data *rdp)
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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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/*
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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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continue;
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/* Exceeded the time limit, so leave. */
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break;
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}
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} else {
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local_bh_enable();
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lockdep_assert_irqs_enabled();
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@ -2535,18 +2546,6 @@ static void rcu_do_batch(struct rcu_data *rdp)
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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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continue;
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/* Exceeded the time limit, so leave. */
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break;
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}
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}
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rcu_nocb_lock_irqsave(rdp, flags);
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