From: Leon Romanovsky <leon@kernel.org>
To: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org, davem@davemloft.net, eric.dumazet@gmail.com
Subject: Re: [RFC net-next 1/2] net: add netdev_refs debug
Date: Wed, 17 Nov 2021 21:27:44 +0200 [thread overview]
Message-ID: <YZVXsETbkjq8U415@unreal> (raw)
In-Reply-To: <20211117103545.189b6d4b@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
On Wed, Nov 17, 2021 at 10:35:45AM -0800, Jakub Kicinski wrote:
> On Wed, 17 Nov 2021 20:24:17 +0200 Leon Romanovsky wrote:
> > > +/* Store a raw, unprotected pointer */
> > > +static inline void __netdev_ref_store(struct netdev_ref *ref,
> > > + struct net_device *dev)
> > > +{
> > > + ref->dev = dev;
> > > +
> > > +#ifdef CONFIG_DEBUG_OBJECTS_NETDEV_REFS
> > > + refcount_set(&ref->cnt, 0);
> >
> > This is very uncommon pattern. I would expect that first pointer access
> > will start from 1, like all refcount_t users. If you still prefer to
> > start from 0, i suggest you to use atomic_t.
>
> It's not really "starting from 0", it's more of a "setting the count
> to invalid". It can't escape from this state with a simple inc.
I understand it and this is what raises eyebrows. The refcount_t type
has very clear semantics which you are stretching too far.
Let's see what Eric had in mind for his RFC.
Thanks
next prev parent reply other threads:[~2021-11-17 19:27 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-17 17:47 [RFC net-next 0/2] explicit netdev refs Jakub Kicinski
2021-11-17 17:47 ` [RFC net-next 1/2] net: add netdev_refs debug Jakub Kicinski
2021-11-17 18:24 ` Leon Romanovsky
2021-11-17 18:35 ` Jakub Kicinski
2021-11-17 19:27 ` Leon Romanovsky [this message]
2021-11-17 19:13 ` Eric Dumazet
2021-11-17 17:47 ` [RFC net-next 2/2] vlan: use new netdev_refs infra Jakub Kicinski
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