Re: [PATCH 1/1] net: Add rtnl_lock for netif_device_attach/detach

[Sergei Shtylyov]

Hello.

On 21-04-2014 10:30, Li, ZhenHua wrote:

> The comment is trying to explain why add a lock here.

   I can read, thanks. :-)
   I was wondering about the kernel-doc comment style you've used; AFAIK, 
it's only good for documenting functions and data structures. The normal 
multi-line comment style in the networking code is this:

/* bla
 * bla
 */

> > > From: "Li, Zhen-Hua" <zhen-hual@xxxxxx>

> > > As netif_running is called in netif_device_attach/detach. There should be
> > > rtnl_lock/unlock called, to avoid dev stat change during netif_device_attach
> > > and detach being called.
> > > I checked NIC some drivers,  some of them have netif_device_attach/detach
> > > called between rtnl_lock/unlock, while some drivers do not.

> > > This patch is tring to find a generic way to fix this for all NIC drivers.

> > > Signed-off-by: Li, Zhen-Hua <zhen-hual@xxxxxx>
> > > ---
> > >   net/core/dev.c |   18 ++++++++++++++++++
> > >   1 file changed, 18 insertions(+)

> > > diff --git a/net/core/dev.c b/net/core/dev.c
> > > index 5b3042e..795bbc5 100644
> > > --- a/net/core/dev.c
> > > +++ b/net/core/dev.c
> > > @@ -2190,10 +2190,19 @@ EXPORT_SYMBOL(__dev_kfree_skb_any);
> > >    */
> > >   void netif_device_detach(struct net_device *dev)
> > >   {
> > > +    /**

> >   Hm, why kernel-doc style comment here?

> > > +     * As netif_running is called , rtnl_lock and unlock are needed to

   Space before comma not needed.

> > > +     * avoid __LINK_STATE_START bit changes during this function call.
> > > +     */
> > > +    int need_unlock;
> > > +
> > > +    need_unlock = rtnl_trylock();
> > >       if (test_and_clear_bit(__LINK_STATE_PRESENT, &dev->state) &&
> > >           netif_running(dev)) {
> > >           netif_tx_stop_all_queues(dev);
> > >       }
> > > +    if (need_unlock)
> > > +        rtnl_unlock();
> > >   }
> > >   EXPORT_SYMBOL(netif_device_detach);
> > >
> > > @@ -2205,11 +2214,20 @@ EXPORT_SYMBOL(netif_device_detach);
> > >    */
> > >   void netif_device_attach(struct net_device *dev)
> > >   {
> > > +    /**

> >   ... and here?

> > > +     * As netif_running is called , rtnl_lock and unlock are needed to

   Space before comma not needed.

> > > +     * avoid __LINK_STATE_START bit changes during this function call.
> > > +     */

WBR, Sergei

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