linux-kernel - Re: [PATCH 1/2 v2] WARN_ON_SMP(): Allow use in if statements on UP

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Message-ID: <1300450473.16880.1476.camel@gandalf.stny.rr.com>
Date:	Fri, 18 Mar 2011 08:14:33 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Darren Hart <dvhart@...ux.intel.com>
Subject: Re: [PATCH 1/2 v2] WARN_ON_SMP(): Allow use in if statements on UP

On Fri, 2011-03-18 at 10:12 +0100, Peter Zijlstra wrote:
> On Thu, 2011-03-17 at 17:56 -0400, Steven Rostedt wrote:
> > + * WARN_ON(!spin_is_locked(&lock)) checks, as spin_is_locked()
> > + * returns 0 for uniprocessor settings. 
> 
> Arguably most spin_is_locked() usages should be removed in favour of
> something like lockdep_assert_held().
> 
> The latter only emits code then built with lockdep enabled and it checks
> we are indeed the owner, not some random other cpu.
> 

Perhaps we should have lockdep_assert_held() also be in
"spin_is_locked()". The warning with spin_is_locked() is still nice to
have because it can trigger on production systems that might find a code
path that it's not locked. lockdep is too heavy to run on production
systems. But if lockdep is enabled, the spin_is_locked() should probably
check ownership too.

-- Steve


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