rcutree/rcu_bh_qs: disable irq while calling rcu_preempt_qs()
Any callers to the function rcu_preempt_qs() must disable irqs in order to protect the assignment to ->rcu_read_unlock_special. In RT case, rcu_bh_qs() as the wrapper of rcu_preempt_qs() is called in some scenarios where irq is enabled, like this path, do_single_softirq() | + local_irq_enable(); + handle_softirq() | | | + rcu_bh_qs() | | | + rcu_preempt_qs() | + local_irq_disable() So here we'd better disable irq directly inside of rcu_bh_qs() to fix this, otherwise the kernel may be freezable sometimes as observed. And especially this way is also kind and safe for the potential rcu_bh_qs() usage elsewhere in the future. Cc: stable-rt@vger.kernel.org Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com> Signed-off-by: Bin Jiang <bin.jiang@windriver.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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@ -204,7 +204,12 @@ static void rcu_preempt_qs(int cpu);
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void rcu_bh_qs(int cpu)
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{
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unsigned long flags;
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/* Callers to this function, rcu_preempt_qs(), must disable irqs. */
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local_irq_save(flags);
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rcu_preempt_qs(cpu);
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local_irq_restore(flags);
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}
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#else
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void rcu_bh_qs(int cpu)
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