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 <[email protected]> Signed-off-by: Paul E. McKenney <[email protected]> --- kernel/rcu/tree.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 61a97164abcc..cac24f5d3fd2 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -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; -- 2.5.2
