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Commit fa3c6647 authored by Paul E. McKenney's avatar Paul E. McKenney
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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: default avatarVegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 752de307

kernel/rcu/tree.c

+7 −2
Original line number Diff line number Diff line
@@ -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;