Re: [PATCH 2/3] livepatch: Avoid blocking tasklist_lock too long

[Josh Poimboeuf <jpoimboe@kernel.org>]

On Wed, Feb 12, 2025 at 07:54:21PM +0800, Yafang Shao wrote:
> Before the newly forked task is added to the task list, it doesn’t
> execute any code and can always be considered safe during the KLP
> transition. Therefore, we could replace klp_copy_process() with
> klp_init_process(), where we simply set patch_state to
> KLP_TRANSITION_IDLE, as shown below:
> 
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -2544,7 +2544,9 @@ __latent_entropy struct task_struct *copy_process(
>                 p->exit_signal = args->exit_signal;
>         }
> 
> -       klp_copy_process(p);
> +       // klp_init_process(p);
> +       clear_tsk_thread_flag(child, TIF_PATCH_PENDING);
> +       child->patch_state = KLP_TRANSITION_IDLE;
> 
>         sched_core_fork(p);
> 
> Some additional changes may be needed, such as removing
> WARN_ON_ONCE(patch_state == KLP_TRANSITION_IDLE) in
> klp_ftrace_handler().

Oops, I managed to miss this email before my reply.  Looks like we had a
similar idea :-)

-- 
Josh