linux-kernel - Re: Is spin_is_locked() safe to use with BUG_ON()/WARN

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Message-ID: <519EC282.1010800@gmail.com>
Date:	Fri, 24 May 2013 11:29:38 +1000
From:	Ryan Mallon <rmallon@...il.com>
To:	David Howells <dhowells@...hat.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>, milosz@...in.com,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Is spin_is_locked() safe to use with BUG_ON()/WARN_ON()?

On 24/05/13 01:12, David Howells wrote:
> Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> 
>> We do *not* want to add some crazy "spin_is_nt_locked". We just want
>> to get rid of these idiotic debug tests.
> 
> Generally, I think you are right, though there are also some checks in
> deallocation routines that check that a spinlock is not currently held before
> releasing the memory holding it - should those be allowed to stay?  I'd be
> tempted to wrap the whole check in something, perhaps an "spin_lock_uninit()"
> and move the check to a header file.  Would this be useful for lockdep or
> anything like that?

lockdep has lockdep_assert_held(), which might be what you want. Though
it looks like it possibly also has the false positive issues on SMP?

~Ryan

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