On Wed, Jul 05, 2023 at 03:30:19PM +0800, Zhen Lei wrote:
> The above condition "if (gpk)" already ensures that gp_kthread is created,
> so the local variable 'cpu' cannot be negative here.
>
> Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
> ---
> kernel/rcu/tree_stall.h | 12 +++++-------
> 1 file changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
> index b10b8349bb2a48b..dcfaa3d5db2cbc7 100644
> --- a/kernel/rcu/tree_stall.h
> +++ b/kernel/rcu/tree_stall.h
> @@ -537,13 +537,11 @@ static void rcu_check_gp_kthread_starvation(void)
> pr_err("\tUnless %s kthread gets sufficient CPU time, OOM is now expected behavior.\n", rcu_state.name);
> pr_err("RCU grace-period kthread stack dump:\n");
> sched_show_task(gpk);
> - if (cpu >= 0) {
I am not quite this trusting of the relation between the relationship
between the existence of the grace-period khread and its CPU number
being in range. Let's please start with something like this:
if (!WARN_ON_ONCE(cpu < 0)) {
Please note that this is not just me. See for example the use of the
cpumask_check() function, albeit the opposite concern.
> - if (cpu_is_offline(cpu)) {
> - pr_err("RCU GP kthread last ran on offline CPU %d.\n", cpu);
> - } else {
> - pr_err("Stack dump where RCU GP kthread last ran:\n");
> - dump_cpu_task(cpu);
> - }
> + if (cpu_is_offline(cpu)) {
> + pr_err("RCU GP kthread last ran on offline CPU %d.\n", cpu);
> + } else {
> + pr_err("Stack dump where RCU GP kthread last ran:\n");
> + dump_cpu_task(cpu);
> }
> wake_up_process(gpk);
> }
> --
> 2.25.1
>
