From: Ben Hutchings <ben@decadent.org.uk>
To: David Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Subject: Re: [PATCH net-2.6] 3c59x: Remove incorrect locking; correct documented lock hierarchy
Date: Wed, 01 Sep 2010 23:08:27 +0100 [thread overview]
Message-ID: <1283378907.5323.287.camel@localhost> (raw)
In-Reply-To: <1283377631.5323.285.camel@localhost>
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On Wed, 2010-09-01 at 22:47 +0100, Ben Hutchings wrote:
> On Wed, 2010-09-01 at 14:38 -0700, David Miller wrote:
> > From: Ben Hutchings <ben@decadent.org.uk>
> > Date: Tue, 31 Aug 2010 01:15:33 +0100
> >
> > > vortex_ioctl() was grabbing vortex_private::lock around its call to
> > > generic_mii_ioctl(). This is no longer necessary since there are more
> > > specific locks which the mdio_{read,write}() functions will obtain.
> > > Worse, those functions do not save and restore IRQ flags when locking
> > > the MII state, so interrupts will be enabled when generic_mii_ioctl()
> > > returns.
> > >
> > > Since there is currently no need for any function to call
> > > mdio_{read,write}() while holding another spinlock, do not change them
> > > to save and restore IRQ flags but remove the specification of ordering
> > > between vortex_private::lock and vortex_private::mii_lock.
> > >
> > > Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> > > ---
> > > I've now borrowed a card to test 3c59x on. I've seen another regression
> > > reported <http://bugs.debian.org/586967> after my locking changes, which
> > > I can't reproduce.
> >
> > I think the lock is necessary, in some form.
> >
> > Nothing otherwise protects vp->mii, which is accessed and modified by
> > not just this ioctl, but also ethtool operation calls.
> >
> > So we can't apply your patch as-is.
>
> Hmm, yes, I forgot that mii caches information in struct mii_if_info.
> Let me rethink this.
I think this is safe after all because ethtool and MII ioctls are all
serialised by the RTNL.
Ben.
--
Ben Hutchings
Once a job is fouled up, anything done to improve it makes it worse.
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next prev parent reply other threads:[~2010-09-01 22:09 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-31 0:15 [PATCH net-2.6] 3c59x: Remove incorrect locking; correct documented lock hierarchy Ben Hutchings
2010-09-01 21:38 ` David Miller
2010-09-01 21:47 ` Ben Hutchings
2010-09-01 22:08 ` Ben Hutchings [this message]
2010-09-02 0:37 ` David Miller
2010-09-02 0:42 ` Ben Hutchings
2010-09-02 1:02 ` David Miller
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