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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-01-04 16:04:01 -0800
committerIngo Molnar <mingo@elte.hu>2010-01-13 09:06:06 +0100
commitcba8244a0f1c277b6b1e48ed6504fa434119e24d (patch)
treebecfa7d6f653774f72f411002626e791243e5057 /kernel/rcutree_plugin.h
parentf9094d8e5587cf21091a9516628147c0b55e4264 (diff)
downloadlwn-cba8244a0f1c277b6b1e48ed6504fa434119e24d.tar.gz
lwn-cba8244a0f1c277b6b1e48ed6504fa434119e24d.zip
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: Paul 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: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/rcutree_plugin.h')
-rw-r--r--kernel/rcutree_plugin.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index f11ebd44b454..e77cdf321e13 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -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);