Commit b4b7914a authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Make call_rcu() print mem_dump_obj() info for double-freed callback 



The debug-object double-free checks in __call_rcu() print out the
RCU callback function, which is usually sufficient to track down the
double free.  However, all uses of things like queue_rcu_work() will
have the same RCU callback function (rcu_work_rcufn() in this case),
so a diagnostic message for a double queue_rcu_work() needs more than
just the callback function.

This commit therefore calls mem_dump_obj() to dump out any additional
available information on the double-freed callback.

Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: <linux-mm@kvack.org>
Reported-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Tested-by: default avatarNaresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent bd34dcd4

kernel/rcu/tree.c

+5 −2
Original line number Diff line number Diff line
@@ -2941,6 +2941,7 @@ static void check_cb_ovld(struct rcu_data *rdp) 
static void

__call_rcu(struct rcu_head *head, rcu_callback_t func)

{

	static atomic_t doublefrees;

	unsigned long flags;

	struct rcu_data *rdp;

	bool was_alldone;
@@ -2954,8 +2955,10 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func) 
		 * 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->%pS()!!!\n",

			  head, head->func);

		if (atomic_inc_return(&doublefrees) < 4) {

			pr_err("%s(): Double-freed CB %p->%pS()!!!  ", __func__, head, head->func);

			mem_dump_obj(head);

		}

		WRITE_ONCE(head->func, rcu_leak_callback);

		return;

	}