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Commit cba8244a authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar
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rcu: Add debug check for too many rcu_read_unlock() 



TREE_PREEMPT_RCU maintains an rcu_read_lock_nesting counter in
the task structure, which happens to be a signed int.  So this
patch adds a check for this counter being negative at the end of
__rcu_read_unlock(). This check is under CONFIG_PROVE_LOCKING,
so can be thought of as being part of lockdep.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <12626498423064-git-send-email->
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent f9094d8e

kernel/rcutree_plugin.h

+3 −0
Original line number Diff line number Diff line
@@ -304,6 +304,9 @@ void __rcu_read_unlock(void) 
	if (--ACCESS_ONCE(t->rcu_read_lock_nesting) == 0 &&

	    unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))

		rcu_read_unlock_special(t);

#ifdef CONFIG_PROVE_LOCKING

	WARN_ON_ONCE(ACCESS_ONCE(t->rcu_read_lock_nesting) < 0);

#endif /* #ifdef CONFIG_PROVE_LOCKING */

}

EXPORT_SYMBOL_GPL(__rcu_read_unlock);