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rcu: Make kfree_rcu() use a non-atomic ->monitor_todo
Because the ->monitor_todo field is always protected by krcp->lock, this commit downgrades from xchg() to non-atomic unmarked assignment statements. Signed-off-by: Joel Fernandes <joel@joelfernandes.org> [ paulmck: Update to include early-boot kick code. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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@ -2708,7 +2708,7 @@ struct kfree_rcu_cpu {
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struct rcu_head *head_free;
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spinlock_t lock;
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struct delayed_work monitor_work;
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int monitor_todo;
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bool monitor_todo;
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bool initialized;
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};
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@ -2765,6 +2765,7 @@ static inline void kfree_rcu_drain_unlock(struct kfree_rcu_cpu *krcp,
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unsigned long flags)
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{
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// Attempt to start a new batch.
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krcp->monitor_todo = false;
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if (queue_kfree_rcu_work(krcp)) {
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// Success! Our job is done here.
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spin_unlock_irqrestore(&krcp->lock, flags);
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@ -2772,8 +2773,8 @@ static inline void kfree_rcu_drain_unlock(struct kfree_rcu_cpu *krcp,
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}
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// Previous RCU batch still in progress, try again later.
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if (!xchg(&krcp->monitor_todo, true))
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schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
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krcp->monitor_todo = true;
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schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
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spin_unlock_irqrestore(&krcp->lock, flags);
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}
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@ -2788,7 +2789,7 @@ static void kfree_rcu_monitor(struct work_struct *work)
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monitor_work.work);
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spin_lock_irqsave(&krcp->lock, flags);
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if (xchg(&krcp->monitor_todo, false))
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if (krcp->monitor_todo)
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kfree_rcu_drain_unlock(krcp, flags);
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else
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spin_unlock_irqrestore(&krcp->lock, flags);
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@ -2837,8 +2838,10 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
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// Set timer to drain after KFREE_DRAIN_JIFFIES.
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if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
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!xchg(&krcp->monitor_todo, true))
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!krcp->monitor_todo) {
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krcp->monitor_todo = true;
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schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
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}
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if (krcp->initialized)
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spin_unlock(&krcp->lock);
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@ -2855,10 +2858,11 @@ void __init kfree_rcu_scheduler_running(void)
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struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
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spin_lock_irqsave(&krcp->lock, flags);
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if (!krcp->head || xchg(&krcp->monitor_todo, true)) {
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if (!krcp->head || krcp->monitor_todo) {
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spin_unlock_irqrestore(&krcp->lock, flags);
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continue;
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}
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krcp->monitor_todo = true;
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schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
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spin_unlock_irqrestore(&krcp->lock, flags);
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}
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