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rcu: Add *_ONCE() to rcu_data ->rcu_forced_tick
The rcu_data structure's ->rcu_forced_tick field is read locklessly, so this commit adds WRITE_ONCE() to all updates and READ_ONCE() to all lockless reads. 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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1 changed files with 4 additions and 3 deletions
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@ -818,11 +818,12 @@ static __always_inline void rcu_nmi_enter_common(bool irq)
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incby = 1;
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} else if (tick_nohz_full_cpu(rdp->cpu) &&
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rdp->dynticks_nmi_nesting == DYNTICK_IRQ_NONIDLE &&
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READ_ONCE(rdp->rcu_urgent_qs) && !rdp->rcu_forced_tick) {
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READ_ONCE(rdp->rcu_urgent_qs) &&
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!READ_ONCE(rdp->rcu_forced_tick)) {
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raw_spin_lock_rcu_node(rdp->mynode);
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// Recheck under lock.
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if (rdp->rcu_urgent_qs && !rdp->rcu_forced_tick) {
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rdp->rcu_forced_tick = true;
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WRITE_ONCE(rdp->rcu_forced_tick, true);
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tick_dep_set_cpu(rdp->cpu, TICK_DEP_BIT_RCU);
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}
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raw_spin_unlock_rcu_node(rdp->mynode);
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@ -899,7 +900,7 @@ static void rcu_disable_urgency_upon_qs(struct rcu_data *rdp)
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WRITE_ONCE(rdp->rcu_need_heavy_qs, false);
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if (tick_nohz_full_cpu(rdp->cpu) && rdp->rcu_forced_tick) {
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tick_dep_clear_cpu(rdp->cpu, TICK_DEP_BIT_RCU);
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rdp->rcu_forced_tick = false;
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WRITE_ONCE(rdp->rcu_forced_tick, false);
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}
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}
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