netdev - Re: [patch 2/4] net: use mutex_is_locked() for ASSERT

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Date:	Sun, 16 Dec 2007 19:06:41 +0100
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Herbert Xu <herbert@...dor.apana.org.au>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [patch 2/4] net: use mutex_is_locked() for ASSERT_RTNL()

Andrew Morton wrote, On 12/15/2007 11:48 AM:

> On Sat, 15 Dec 2007 14:10:21 +0800 Herbert Xu <herbert@...dor.apana.org.au> wrote:
> 
>> On Fri, Dec 14, 2007 at 09:44:18PM -0800, Andrew Morton wrote:
>>> That sounds like a bug in mutex_trylock() to me.
>> I was relying on
>>
>> 	http://kerneltrap.org/mailarchive/linux-netdev/2007/9/28/325129
>>
>> which seems to be a bogus claim now that I actually look at the
>> source code.  So in that case I'm OK with your patch as long as
>> it warns about hard IRQ usage.
> 
> When Eric said
> 
>> Way way deep in mutex debugging on the slowpath there is a unreadable
>> and incomprehensible WARN_ON in muxtex_trylock that will trigger if
>> you have 10 tons of debugging turned on, and you are in,
>> interrupt context, and you manage to hit the slow path.  I think that
>> is a pretty unlikely scenario.
> 
> I think he's still right.  That's if the warning which he managed to find
> even still exists.


It seemed to exist a few days ago:
http://kerneltrap.org/mailarchive/linux-netdev/2007/12/4/473123

Btw., I don't know which of the patches: Eric's or yours will be chosen,
but, IMHO, there is no reason to remove rtnl_trylock(), which can be still
useful, just like mutex_trylock() is.

Regards,
Jarek P.
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