Re: [patch 2/4] net: use mutex_is_locked() for ASSERT_RTNL()

[David Miller <davem@davemloft.net>]

From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Fri, 14 Dec 2007 16:30:37 +0800

> On Fri, Dec 14, 2007 at 12:22:09AM -0800, Andrew Morton wrote:
> >
> > I don't see how it could warn about that.  Nor should it - one might want
> > to check that rtnl_lock is held inside preempt_disable() or spin_lock or
> > whatever.
> > 
> > It might make sense to warn if ASSERT_RTNL is called in in_interrupt()
> > contexts though.
> 
> Well the paths where ASSERT_RTNL is used should never be in an
> atomic context.  In the past it has been quite useful in pointing
> out bogus locking practices.
> 
> There is currently one path where it's known to warn because of
> this and it (promiscuous mode) is on my todo list.
> 
> Oh and it only warns when you have mutex debugging enabled.

Right, this change is just totally bogus.

I'm all for using existing facilities to replace hand-crafted copies,
but this case is removing useful debugging functionality so it's
wrong.