linux-kernel - Re: [patch] sunrpc: make closing of old temporary sockets work (was: problems with lockd in 2.6.22.6)

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Message-Id: <200709130018.55728.wolfgang.walter@studentenwerk.mhn.de>
Date:	Thu, 13 Sep 2007 00:18:55 +0200
From:	Wolfgang Walter <wolfgang.walter@...dentenwerk.mhn.de>
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	Neil Brown <neilb@...e.de>, trond.myklebust@....uio.no,
	netdev@...r.kernel.org, nfs@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] sunrpc: make closing of old temporary sockets work (was: problems with lockd in 2.6.22.6)

On Wednesday 12 September 2007, J. Bruce Fields wrote:
> On Wed, Sep 12, 2007 at 09:40:57PM +0200, Wolfgang Walter wrote:
> > On Wednesday 12 September 2007, J. Bruce Fields wrote:
> > > On Wed, Sep 12, 2007 at 04:14:06PM +0200, Neil Brown wrote:
> > > > So it is in 2.6.21 and later and should probably go to .stable for .21
> > > > and .22.
> > > > 
> > > > Bruce:  for you :-)
> > > 
> > > OK, thanks!  But, (as is alas often the case) I'm still confused:
> > > 
> > > >  		if (!test_and_set_bit(SK_OLD, &svsk->sk_flags))
> > > >  			continue;
> > > > -		if (atomic_read(&svsk->sk_inuse) || test_bit(SK_BUSY, 
&svsk->sk_flags))
> > > > +		if (atomic_read(&svsk->sk_inuse) > 1
> > > > +		    || test_bit(SK_BUSY, &svsk->sk_flags))
> > > >  			continue;
> > > >  		atomic_inc(&svsk->sk_inuse);
> > > >  		list_move(le, &to_be_aged);
> > > 
> > > What is it that ensures svsk->sk_inuse isn't incremented or SK_BUSY set
> > > after that test?  Not all the code that does either of those is under
> > > the same serv->sv_lock lock that this code is.
> > > 
> > 
> > This should not matter - SK_CLOSED may be set at any time.
> > 
> > svc_age_temp_sockets only detaches the socket, sets SK_CLOSED and then 
> > enqueues it. If SK_BUSY is set its already enqueued and svc_sock_enqueue 
> > ensures that it is not enqueued twice.
> 
> Oh, got it.  And the list manipulation is safe thanks to sv_lock.  Neat,
> thanks.  Can you verify that this solves your problem?
> 

I'll test it tomorrow. So friday morning I'll know and mail you for sure.

Regards,
-- 
Wolfgang Walter
Studentenwerk München
Anstalt des öffentlichen Rechts
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