netdev - Re: packet_sendmsg_spkt sleeping from invalid context

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Date:	Mon, 14 Dec 2009 22:30:04 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Neil Horman <nhorman@...driver.com>,
	Netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: packet_sendmsg_spkt sleeping from invalid context

On Mon, Dec 14, 2009 at 10:25:57PM +0100, Eric Dumazet wrote:
> Le 14/12/2009 21:52, Frederic Weisbecker a écrit :
> > 
> > I also wonder. Are you using PREEMPT_RCU ?
> 
> Not at all :)
> 
> But yes, this is illegal to do the memcpy_fromiovec() in rcu_read_lock() context.


I've just tested, and with rcu preempt it is mute, no warning :)


> > That may explain why you haven't seen this issue because
> > might_sleep() doesn't see you are in a rcu read locked
> > section as preemption is not disabled, but it is illegal to
> > voluntarily sleep in such area (although it's fine with
> > preempt rcu) as doing so with non-prempt RCU config would barf.
> > 
> > I'm trying a patch to handle that.
> 
> As you want, I also have a patch testing right now :)


But mine is to teach might_sleep() to handle rcu preempt case,
not to fix this net dev thing.

But I'll happily test the fix you have :)

Thanks.

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