linux-kernel - Re: [PATCH] init: Add lockdep annotation to kthreadd

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Message-Id: <20230811094359.ae44c1081b52f69baad8e651@linux-foundation.org>
Date:   Fri, 11 Aug 2023 09:43:59 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Helge Deller <deller@....de>
Cc:     linux-kernel@...r.kernel.org, linux-parisc@...r.kernel.org,
        Mike Rapoport <rppt@...nel.org>
Subject: Re: [PATCH] init: Add lockdep annotation to kthreadd_done completer

On Fri, 11 Aug 2023 18:04:22 +0200 Helge Deller <deller@....de> wrote:

> Add the missing lockdep annotation to avoid this warning:
> 
>  INFO: trying to register non-static key.
>  The code is fine but needs lockdep annotation, or maybe
>  you didn't initialize this object before use?
>  turning off the locking correctness validator.
>  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.5.0-rc5+ #681
>  Hardware name: 9000/785/C3700
>  Backtrace:
>   [<000000004030bcd0>] show_stack+0x74/0xb0
>   [<0000000041469c7c>] dump_stack_lvl+0x104/0x180
>   [<0000000041469d2c>] dump_stack+0x34/0x48
>   [<000000004040e5b4>] register_lock_class+0xd24/0xd30
>   [<000000004040c21c>] __lock_acquire.isra.0+0xb4/0xac8
>   [<000000004040cd60>] lock_acquire+0x130/0x298
>   [<000000004146df54>] _raw_spin_lock_irq+0x60/0xb8
>   [<0000000041472044>] wait_for_completion+0xa0/0x2d0
>   [<000000004146b544>] kernel_init+0x48/0x3a8
>   [<0000000040302020>] ret_from_kernel_thread+0x20/0x28
> 
> ...
>
> --- a/init/main.c
> +++ b/init/main.c
> @@ -682,6 +682,8 @@ noinline void __ref __noreturn rest_init(void)
>  	struct task_struct *tsk;
>  	int pid;
> 
> +	init_completion(&kthreadd_done);
> +
>  	rcu_scheduler_starting();
>  	/*
>  	 * We need to spawn init first so that it obtains pid 1, however

This is pretty old code, as is the page_alloc_init_late() change.  Do
we know why this warning has just turned up lately?

I'll add cc:stable to these, but might take that away again if we can
answer the above.

btw, please don't forget the "^---$" between changelog and patch.