linux-kernel - Re: [PATCH] sgi-xp: Do not use BUG_ON(!spin_is

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Date:	Wed, 20 Aug 2014 09:04:19 +1000
From:	Ryan Mallon <rmallon@...il.com>
To:	Sanjeev Sharma <sanjeev_sharma@...tor.com>, cpw@....com,
	robinmholt@...il.com
CC:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sgi-xp: Do not use BUG_ON(!spin_is_locked())

On 12/08/14 17:35, Sanjeev Sharma wrote:
> on some architecture spin_is_locked() always return false in
> uniprocessor configuration and can therefore not be used
> with BUG_ON.it would be advise to replace with
> lockdep_assert_held().
> 
> Signed-off-by: Sanjeev Sharma <Sanjeev_Sharma@...tor.com>
> ---
>  drivers/misc/sgi-xp/xpc_channel.c | 6 +++---
>  drivers/misc/sgi-xp/xpc_sn2.c     | 2 +-
>  drivers/misc/sgi-xp/xpc_uv.c      | 2 +-
>  3 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/misc/sgi-xp/xpc_channel.c b/drivers/misc/sgi-xp/xpc_channel.c
> index 128d561..240fe5a 100644
> --- a/drivers/misc/sgi-xp/xpc_channel.c
> +++ b/drivers/misc/sgi-xp/xpc_channel.c
> @@ -28,7 +28,7 @@ xpc_process_connect(struct xpc_channel *ch, unsigned long *irq_flags)
>  {
>  	enum xp_retval ret;
>  
> -	DBUG_ON(!spin_is_locked(&ch->lock));
> +	lockdep_assert_held(!spin_is_locked(&ch->lock));

This is incorrect, and will break the build with CONFIG_LOCKDEP enabled.
You actually want:

	lockdep_assert_held(&ch->lock);

Same for the other instances.

~Ryan
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