linux-kernel - Re: [for-next][PATCH 6/7] ring-buffer: Process commits whenever moving to a new page.

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Date:	Wed, 25 Nov 2015 15:22:26 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [for-next][PATCH 6/7] ring-buffer: Process commits whenever
 moving to a new page.


> diff --git a/kernel/module.c b/kernel/module.c
> index 8f051a106676..c0ae7c18c2fa 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -284,11 +284,25 @@ static void module_assert_mutex(void)
>  static void module_assert_mutex_or_preempt(void)
>  {
>  #ifdef CONFIG_LOCKDEP
> +	static int once;
> +
>  	if (unlikely(!debug_locks))
>  		return;
>  
> -	WARN_ON(!rcu_read_lock_sched_held() &&
> -		!lockdep_is_held(&module_mutex));
> +	/*
> +	 * Would be nice to use WARN_ON_ONCE(), but the warning
> +	 * that causes a stack trace may call __module_address()
> +	 * which may call here, and we trigger the warning again,
> +	 * before the WARN_ON_ONCE() updates its flag.
> +	 * To prevent the recursion, we need to open code the
> +	 * once logic.
> +	 */
> +	if (!once &&
> +	    unlikely(!rcu_read_lock_sched_held() &&
> +		     !lockdep_is_held(&module_mutex))) {
> +		once++;
> +		WARN_ON(1);
> +	}
>  #endif
>  }
>  
>

Damn it. I added this via quilt to debug something (as this was causing
a crash), and forgot to pop it when doing my "git commit -a -s".

I'll have to nuke this part of the patch and rebase my tree :-(

-- Steve
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