netdev - Re: [PATCH 3/4] 8139too: RTNL and flush_scheduled

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Date:	Fri, 16 Feb 2007 21:20:34 +0100
From:	Francois Romieu <romieu@...zoreil.com>
To:	Jarek Poplawski <jarkao2@...pl>
Cc:	jeff@...zik.org,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	akpm@...ux-foundation.org, netdev@...r.kernel.org,
	Ben Greear <greearb@...delatech.com>,
	Kyle Lucke <klucke@...ibm.com>,
	Raghavendra Koushik <raghavendra.koushik@...erion.com>,
	Al Viro <viro@....linux.org.uk>
Subject: Re: [PATCH 3/4] 8139too: RTNL and flush_scheduled_work deadlock

Jarek Poplawski <jarkao2@...pl> :
[...]
> > diff --git a/drivers/net/8139too.c b/drivers/net/8139too.c
> > index 35ad5cf..99304b2 100644
> > --- a/drivers/net/8139too.c
> > +++ b/drivers/net/8139too.c
> > @@ -1109,6 +1109,8 @@ static void __devexit rtl8139_remove_one (struct pci_dev *pdev)
> >  
> >  	assert (dev != NULL);
> >  
> > +	flush_scheduled_work();
> > +
> 
> IMHO there should be rather cancel_rearming_delayed_work
> instead of this.

The delayed_work is initialized even if tp->have_thread is false,
so cancel_rearming_delayed_work() will work, yes. Feel free to
send a patch.

[...]
> > @@ -1603,18 +1605,21 @@ static void rtl8139_thread (struct work_struct *work)
> >  	struct net_device *dev = tp->mii.dev;
> >  	unsigned long thr_delay = next_tick;
> >  
> > +	rtnl_lock();
> > +
> > +	if (!netif_running(dev))
> > +		goto out_unlock;
> 
> I wonder, why you don't do netif_running before
> rtnl_lock ? It's an atomic operation. And I'm not sure if increasing
> rtnl_lock range is really needed here.

thread    A: netif_running()
user task B: rtnl_lock()
user task B: dev->close()
user task B: rtnl_unlock()
thread    A: rtnl_lock()
thread    A: mess with closed device

Btw, the thread runs every 3*HZ at most.

-- 
Ueimor
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