netdev - Re: net-next/unix: BUG: using smp_processor

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Date:	Sun, 23 Nov 2008 23:40:32 +0200 (EET)
From:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
To:	Eric Dumazet <dada1@...mosbay.com>
cc:	David Miller <davem@...emloft.net>, Netdev <netdev@...r.kernel.org>
Subject: Re: net-next/unix: BUG: using smp_processor_id() in preemptible

On Sun, 23 Nov 2008, Eric Dumazet wrote:

> Ilpo Järvinen a écrit :
> > I got plenty of these from sock_prot_inuse_add:
> > 
> > BUG: using smp_processor_id() in preemptible [00000000] code: rcS/1146
> > 
> > caller is sock_prot_inuse_add+0x24/0x42
> > Pid: 1146, comm: rcS Not tainted 2.6.28-rc6-01121-g89a2f15 #76
> > Call Trace:
> >  [<ffffffff80365767>] debug_smp_processor_id+0xd3/0xe8
> >  [<ffffffff80485a0f>] sock_prot_inuse_add+0x24/0x42
> >  [<ffffffff80514cdd>] unix_create1+0x161/0x176
> >  [<ffffffff80514d52>] unix_create+0x60/0x6b
> >  [<ffffffff80483f66>] __sock_create+0x144/0x1bd
> >  [<ffffffff80483edb>] ? __sock_create+0xb9/0x1bd
> >  [<ffffffff8048402d>] sock_create+0x2d/0x2f
> >  [<ffffffff80484274>] sys_socket+0x29/0x5b
> >  [<ffffffff8020c10a>] system_call_fastpath+0x16/0x1b
> > 
> > 
> 
> Thanks Ilpo for this report
> 
> I guess the following is necessary.
> 
> Once Christopher and Rusty work on percpu variables is finished,
> the preempt_enable()/disable() wont be necessary anymore, so
> its a temporary workaround anyway.
> 
> [PATCH] net: make sock_prot_inuse_add() preempt safe
> 
> Ilpo Järvinen reported that commit a8076d8db98de6da61394b2e942320e4612643ac
> (net: af_unix should update its inuse counter) was triggering
> a warning in smp_processor_id(), being called in a preemptible code.
> 
> Fix is to make sock_prot_inuse_add() safe in this regard. This fix
> can be reverted when new percpu infrastructure is ready, allowing
> a cpu to safely do a increment/decrement on a percpu var.
> 
> Signed-off-by: Eric Dumazet <dada1@...mosbay.com>

Works.

Tested-by: Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>

-- 
 i.