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

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Message-Id: <20071214002209.ac748206.akpm@linux-foundation.org>
Date:	Fri, 14 Dec 2007 00:22:09 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [patch 2/4] net: use mutex_is_locked() for ASSERT_RTNL()

On Fri, 14 Dec 2007 16:10:44 +0800 Herbert Xu <herbert@...dor.apana.org.au> wrote:

> akpm@...ux-foundation.org wrote:
> >
> > diff -puN drivers/net/cxgb3/cxgb3_main.c~net-use-mutex_is_locked-for-assert_rtnl drivers/net/cxgb3/cxgb3_main.c
> > --- a/drivers/net/cxgb3/cxgb3_main.c~net-use-mutex_is_locked-for-assert_rtnl
> > +++ a/drivers/net/cxgb3/cxgb3_main.c
> > @@ -2191,7 +2191,7 @@ static void check_t3b2_mac(struct adapte
> > {
> >        int i;
> > 
> > -       if (!rtnl_trylock())    /* synchronize with ifdown */
> > +       if (rtnl_is_locked())   /* synchronize with ifdown */
> >                return;
> > 
> >        for_each_port(adapter, i) {
> > @@ -2219,7 +2219,6 @@ static void check_t3b2_mac(struct adapte
> >                        p->mac.stats.num_resets++;
> >                }
> >        }
> > -       rtnl_unlock();
> 
> This doesn't look right.  It seems that they really want trylock
> here so we should just fix it by removing the bang.

doh.

> Also, does ASSERT_RTNL still warn when someone calls it from an
> atomic context? We definitely don't want to lose that check.

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.

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