rcu: Improve diagnostics for blocked critical sections in irq
If an RCU read-side critical section occurs within an interrupt handler or a softirq handler, it cannot have been preempted. Therefore, there is a check in rcu_read_unlock_special() checking for this error. However, when this check triggers, it lacks diagnostic information. This commit therefore moves rcu_read_unlock()'s lockdep annotation to follow the call to __rcu_read_unlock() and changes rcu_read_unlock_special()'s WARN_ON_ONCE() to an lockdep_rcu_suspicious() in order to locate where the offending RCU read-side critical section began. In addition, the value of the ->rcu_read_unlock_special field is printed. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Родитель
6629240575
Коммит
d24209bb68
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@ -531,8 +531,13 @@ do { \
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# define might_lock_read(lock) do { } while (0)
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#endif
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#ifdef CONFIG_PROVE_RCU
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#ifdef CONFIG_LOCKDEP
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void lockdep_rcu_suspicious(const char *file, const int line, const char *s);
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#else
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static inline void
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lockdep_rcu_suspicious(const char *file, const int line, const char *s)
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{
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}
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#endif
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#endif /* __LINUX_LOCKDEP_H */
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@ -942,9 +942,9 @@ static inline void rcu_read_unlock(void)
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{
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rcu_lockdep_assert(rcu_is_watching(),
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"rcu_read_unlock() used illegally while idle");
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rcu_lock_release(&rcu_lock_map);
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__release(RCU);
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__rcu_read_unlock();
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rcu_lock_release(&rcu_lock_map); /* Keep acq info for rls diags. */
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}
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/**
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@ -334,7 +334,13 @@ void rcu_read_unlock_special(struct task_struct *t)
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}
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/* Hardware IRQ handlers cannot block, complain if they get here. */
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if (WARN_ON_ONCE(in_irq() || in_serving_softirq())) {
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if (in_irq() || in_serving_softirq()) {
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lockdep_rcu_suspicious(__FILE__, __LINE__,
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"rcu_read_unlock() from irq or softirq with blocking in critical section!!!\n");
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pr_alert("->rcu_read_unlock_special: %#x (b: %d, nq: %d)\n",
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t->rcu_read_unlock_special.s,
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t->rcu_read_unlock_special.b.blocked,
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t->rcu_read_unlock_special.b.need_qs);
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local_irq_restore(flags);
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return;
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}
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