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rcu: Improve __call_rcu() debug-objects error message 

The "__call_rcu(): Leaked duplicate callback" error message from
__call_rcu() has proven to be unhelpful.  This commit therefore changes
it to "__call_rcu(): Double-freed CB" and adds the value of the pointer
passed in.  The value of the pointer improves debuggability by allowing
correlation with tracing output, for example, the rcu:rcu_callback trace
event.

Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2017-05-03 11:38:55 -07:00
parent 752de307b0
commit fa3c664769
1 changed files with 7 additions and 2 deletions
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9
kernel/rcu/tree.c
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@ -3161,9 +3161,14 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func,
WARN_ON_ONCE((unsigned long)head & (sizeof(void *) - 1));
if (debug_rcu_head_queue(head)) {
/* Probable double call_rcu(), so leak the callback. */
/*
* Probable double call_rcu(), so leak the callback.
* Use rcu:rcu_callback trace event to find the previous
* time callback was passed to __call_rcu().
*/
WARN_ONCE(1, "__call_rcu(): Double-freed CB %p->%pF()!!!\n",
head, head->func);
WRITE_ONCE(head->func, rcu_leak_callback);
WARN_ONCE(1, "__call_rcu(): Leaked duplicate callback\n");
return;
}
head->func = func;