Commit fa3c6647 authored by Paul E. McKenney's avatar Paul E. McKenney

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
Reported-by: default avatarVegard Nossum <>
Signed-off-by: default avatarPaul E. McKenney <>
parent 752de307
......@@ -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");
head->func = func;
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