On Tue, Aug 27, 2019 at 03:01:57PM -0400, Joel Fernandes (Google) wrote:
> Make use of RCU's debug_objects debugging support
> (CONFIG_DEBUG_OBJECTS_RCU_HEAD) similar to call_rcu() and other flavors.
Other flavors? Ah, call_srcu(), rcu_barrier(), and srcu_barrier(),
right?
> We queue the object during the kfree_rcu() call and dequeue it during
> reclaim.
>
> Tested that enabling CONFIG_DEBUG_OBJECTS_RCU_HEAD successfully detects
> double kfree_rcu() calls.
>
> Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
The code looks good!
Thanx, Paul
> ---
> kernel/rcu/tree.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 9b9ae4db1c2d..64568f12641d 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -2757,6 +2757,7 @@ static void kfree_rcu_work(struct work_struct *work)
> for (; head; head = next) {
> next = head->next;
> /* Could be possible to optimize with kfree_bulk in future */
> + debug_rcu_head_unqueue(head);
> __rcu_reclaim(rcu_state.name, head);
> cond_resched_tasks_rcu_qs();
> }
> @@ -2868,6 +2869,13 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
> if (rcu_scheduler_active != RCU_SCHEDULER_RUNNING)
> return kfree_call_rcu_nobatch(head, func);
>
> + if (debug_rcu_head_queue(head)) {
> + /* Probable double kfree_rcu() */
> + WARN_ONCE(1, "kfree_call_rcu(): Double-freed call. rcu_head %p\n",
> + head);
> + return;
> + }
> +
> head->func = func;
>
> local_irq_save(flags); /* For safely calling this_cpu_ptr(). */
> --
> 2.23.0.187.g17f5b7556c-goog
>
