linux-kernel - Re: [PATCH] devtmpfs: Add missing lockdep annotation

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Date:   Sat, 12 Aug 2023 13:11:17 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Helge Deller <deller@....de>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org, linux-parisc@...r.kernel.org
Subject: Re: [PATCH] devtmpfs: Add missing lockdep annotation

On Fri, Aug 11, 2023 at 06:02:29PM +0200, Helge Deller wrote:
> Add the lockdep annotation to the setup_done completer to avoid this
> kernel warning:
> 
>  Backtrace:
>   [<000000004030bcd0>] show_stack+0x74/0xb0
>   [<000000004146c63c>] dump_stack_lvl+0x104/0x180
>   [<000000004146c6ec>] dump_stack+0x34/0x48
>   [<000000004040e5b4>] register_lock_class+0xd24/0xd30
>   [<000000004040c21c>] __lock_acquire.isra.0+0xb4/0xac8
>   [<000000004040cd60>] lock_acquire+0x130/0x298
>   [<000000004147095c>] _raw_spin_lock_irq+0x60/0xb8
>   [<0000000041474a4c>] wait_for_completion+0xa0/0x2d0
>   [<000000004015d9f4>] devtmpfs_init+0x1e0/0x2b8
>   [<000000004015d0e4>] driver_init+0x68/0x1b8
>   [<0000000040102b68>] kernel_init_freeable+0x4ac/0x7f0
>   [<000000004146df68>] kernel_init+0x64/0x3a8
>   [<0000000040302020>] ret_from_kernel_thread+0x20/0x28
> 
> Signed-off-by: Helge Deller <deller@....de>
> 
> diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
> index b848764ef018..f98d58b0225c 100644
> --- a/drivers/base/devtmpfs.c
> +++ b/drivers/base/devtmpfs.c
> @@ -462,6 +462,7 @@ int __init devtmpfs_init(void)
>  		return err;
>  	}
> 
> +	init_completion(&setup_done);
>  	thread = kthread_run(devtmpfsd, &err, "kdevtmpfs");
>  	if (!IS_ERR(thread)) {
>  		wait_for_completion(&setup_done);

What changed to required this now?  What commit id does this fix?  Why
doesn't the declaration of DECLARE_COMPLETION() initialize this properly
for us already?

thanks,

greg k-h