On Fri, Jul 01, 2022 at 10:44:04AM +0800, Zqiang wrote:
> Currently, only tree RCU support leak callbacks setting when do
> duplicate call_rcu(). this commit add leak callbacks setting when
> fo duplicate call_rcu() for tiny RCU.
>
> Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
This does look plausible, thank you!
What testing have you done?
One important test for Tiny RCU is that the size of the kernel not
grow without a very good reason. In this case, the added code should
be dead code in a production build (CONFIG_DEBUG_OBJECTS_RCU_HEAD=n),
but it is good to check.
It is of course also good to check that the messages print as expected,
which is what rcutorture.object_debug is there to help with.
Thanx, Paul
> ---
> v1->v2:
> for do duplicate kvfree_call_rcu(), not set leak callbacks.
>
> kernel/rcu/tiny.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
> index f0561ee16b9c..943d431b908f 100644
> --- a/kernel/rcu/tiny.c
> +++ b/kernel/rcu/tiny.c
> @@ -158,6 +158,10 @@ void synchronize_rcu(void)
> }
> EXPORT_SYMBOL_GPL(synchronize_rcu);
>
> +static void tiny_rcu_leak_callback(struct rcu_head *rhp)
> +{
> +}
> +
> /*
> * Post an RCU callback to be invoked after the end of an RCU grace
> * period. But since we have but one CPU, that would be after any
> @@ -165,9 +169,20 @@ EXPORT_SYMBOL_GPL(synchronize_rcu);
> */
> void call_rcu(struct rcu_head *head, rcu_callback_t func)
> {
> + static atomic_t doublefrees;
> unsigned long flags;
>
> - debug_rcu_head_queue(head);
> + if (debug_rcu_head_queue(head)) {
> + if (atomic_inc_return(&doublefrees) < 4) {
> + pr_err("%s(): Double-freed CB %p->%pS()!!! ", __func__, head, head->func);
> + mem_dump_obj(head);
> + }
> +
> + if (!__is_kvfree_rcu_offset((unsigned long)head->func))
> + WRITE_ONCE(head->func, tiny_rcu_leak_callback);
> + return;
> + }
> +
> head->func = func;
> head->next = NULL;
>
> --
> 2.25.1
>
