linux-kernel - Re: [PATCH -rt 1/9] preempt rcu: check for underflow

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Message-ID: <20070730092211.GA25640@elte.hu>
Date:	Mon, 30 Jul 2007 11:22:11 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Daniel Walker <dwalker@...sta.com>
Cc:	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: Re: [PATCH -rt 1/9] preempt rcu: check for underflow


* Daniel Walker <dwalker@...sta.com> wrote:

> +	/*
> +	 * If our rcu_read_lock_nesting went negative, likely
> +	 * something is wrong..
> +	 */
> +	WARN_ON(current->rcu_read_lock_nesting < 0);

have you actually caught any rcu locking problem this way? Double 
unlocks should be caught by lockdep already, at a higher level.

in any case i've added a slightly different form of this change to the 
-rt queue that will also check for counter overflows. But i'm not sure 
we want to litter the code with trivial checks like this, so i'm keeping 
it separate and if it does not trigger anything real i'll remove it.

	Ingo
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