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authorMathieu Desnoyers <mathieu.desnoyers@efficios.com>2010-04-17 08:48:42 -0400
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2010-06-14 19:37:26 -0400
commit551d55a944b143ef26fbd482d1c463199d6f65cf (patch)
tree6911d3f8e8719ba5ca43c83acdf87cbc8276d7d1 /kernel/rcutiny.c
parent875352c94224c88f5aa28cb77206f993bd31b7a2 (diff)
tree/tiny rcu: Add debug RCU head objects
Helps finding racy users of call_rcu(), which results in hangs because list entries are overwritten and/or skipped. Changelog since v4: - Bissectability is now OK - Now generate a WARN_ON_ONCE() for non-initialized rcu_head passed to call_rcu(). Statically initialized objects are detected with object_is_static(). - Rename rcu_head_init_on_stack to init_rcu_head_on_stack. - Remove init_rcu_head() completely. Changelog since v3: - Include comments from Lai Jiangshan This new patch version is based on the debugobjects with the newly introduced "active state" tracker. Non-initialized entries are all considered as "statically initialized". An activation fixup (triggered by call_rcu()) takes care of performing the debug object initialization without issuing any warning. Since we cannot increase the size of struct rcu_head, I don't see much room to put an identifier for statically initialized rcu_head structures. So for now, we have to live without "activation without explicit init" detection. But the main purpose of this debug option is to detect double-activations (double call_rcu() use of a rcu_head before the callback is executed), which is correctly addressed here. This also detects potential internal RCU callback corruption, which would cause the callbacks to be executed twice. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> CC: David S. Miller <davem@davemloft.net> CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> CC: akpm@linux-foundation.org CC: mingo@elte.hu CC: laijs@cn.fujitsu.com CC: dipankar@in.ibm.com CC: josh@joshtriplett.org CC: dvhltc@us.ibm.com CC: niv@us.ibm.com CC: tglx@linutronix.de CC: peterz@infradead.org CC: rostedt@goodmis.org CC: Valdis.Kletnieks@vt.edu CC: dhowells@redhat.com CC: eric.dumazet@gmail.com CC: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Diffstat (limited to 'kernel/rcutiny.c')
-rw-r--r--kernel/rcutiny.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index 38729d3cd236..196ec02f8be0 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -169,6 +169,7 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
169 while (list) { 169 while (list) {
170 next = list->next; 170 next = list->next;
171 prefetch(next); 171 prefetch(next);
172 debug_rcu_head_unqueue(list);
172 list->func(list); 173 list->func(list);
173 list = next; 174 list = next;
174 } 175 }
@@ -211,6 +212,7 @@ static void __call_rcu(struct rcu_head *head,
211{ 212{
212 unsigned long flags; 213 unsigned long flags;
213 214
215 debug_rcu_head_queue(head);
214 head->func = func; 216 head->func = func;
215 head->next = NULL; 217 head->next = NULL;
216 218