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rcu: Add *_ONCE() to rcu_node ->boost_kthread_status
The rcu_node structure's ->boost_kthread_status field is accessed locklessly, so this commit causes all updates to use WRITE_ONCE() and all reads to use READ_ONCE(). This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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@ -1032,18 +1032,18 @@ static int rcu_boost_kthread(void *arg)
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trace_rcu_utilization(TPS("Start boost kthread@init"));
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trace_rcu_utilization(TPS("Start boost kthread@init"));
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for (;;) {
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for (;;) {
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rnp->boost_kthread_status = RCU_KTHREAD_WAITING;
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WRITE_ONCE(rnp->boost_kthread_status, RCU_KTHREAD_WAITING);
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trace_rcu_utilization(TPS("End boost kthread@rcu_wait"));
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trace_rcu_utilization(TPS("End boost kthread@rcu_wait"));
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rcu_wait(rnp->boost_tasks || rnp->exp_tasks);
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rcu_wait(rnp->boost_tasks || rnp->exp_tasks);
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trace_rcu_utilization(TPS("Start boost kthread@rcu_wait"));
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trace_rcu_utilization(TPS("Start boost kthread@rcu_wait"));
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rnp->boost_kthread_status = RCU_KTHREAD_RUNNING;
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WRITE_ONCE(rnp->boost_kthread_status, RCU_KTHREAD_RUNNING);
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more2boost = rcu_boost(rnp);
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more2boost = rcu_boost(rnp);
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if (more2boost)
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if (more2boost)
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spincnt++;
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spincnt++;
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else
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else
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spincnt = 0;
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spincnt = 0;
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if (spincnt > 10) {
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if (spincnt > 10) {
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rnp->boost_kthread_status = RCU_KTHREAD_YIELDING;
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WRITE_ONCE(rnp->boost_kthread_status, RCU_KTHREAD_YIELDING);
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trace_rcu_utilization(TPS("End boost kthread@rcu_yield"));
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trace_rcu_utilization(TPS("End boost kthread@rcu_yield"));
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schedule_timeout_interruptible(2);
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schedule_timeout_interruptible(2);
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trace_rcu_utilization(TPS("Start boost kthread@rcu_yield"));
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trace_rcu_utilization(TPS("Start boost kthread@rcu_yield"));
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@ -1082,7 +1082,7 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
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rnp->boost_tasks = rnp->gp_tasks;
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rnp->boost_tasks = rnp->gp_tasks;
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raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
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raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
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rcu_wake_cond(rnp->boost_kthread_task,
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rcu_wake_cond(rnp->boost_kthread_task,
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rnp->boost_kthread_status);
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READ_ONCE(rnp->boost_kthread_status));
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} else {
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} else {
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raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
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raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
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}
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}
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