Re: [PATCH 3/8] rcu/exp: Fix RCU expedited parallel grace period kworker allocation failure recovery

Kalesh Singh
2023-12-12T16:04:27Z

On Fri, Dec 8, 2023 at 5:06 PM Frederic Weisbecker <frederic@kernel.org> wrote:
>
> Under CONFIG_RCU_EXP_KTHREAD=y, the nodes initialization for expedited
> grace periods is queued to a kworker. However if the allocation of that
> kworker failed, the nodes initialization is performed synchronously by
> the caller instead.
>
> Now the check for kworker initialization failure relies on the kworker
> pointer to be NULL while its value might actually encapsulate an
> allocation failure error.
>
> Make sure to handle this case.
>
> Fixes: 9621fbee44df ("rcu: Move expedited grace period (GP) work to RT kthread_worker")
> Cc: Kalesh Singh <kaleshsingh@google.com>
> Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
> ---
> kernel/rcu/tree.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 82f8130d3fe3..055f4817bc70 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -4723,6 +4723,7 @@ static void __init rcu_start_exp_gp_kworkers(void)
> rcu_exp_par_gp_kworker = kthread_create_worker(0, par_gp_kworker_name);
> if (IS_ERR_OR_NULL(rcu_exp_par_gp_kworker)) {
> pr_err("Failed to create %s!\n", par_gp_kworker_name);
> + rcu_exp_par_gp_kworker = NULL;
> kthread_destroy_worker(rcu_exp_gp_kworker);

Hi Frederic,

Thanks for catching this. I think we need to remove the
kthread_destroy_worker() in this case too.

Otherwise,

Reviewed-by: Kalesh Singh <kaleshsingh@google.com>

--Kalesh

> return;
> }
> --
> 2.42.1
>