linux-kernel - Re: 2.6.34-rc1: rcu lockdep bug?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1268392276.3141.4.camel@edumazet-laptop>
Date:	Fri, 12 Mar 2010 12:11:16 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Américo Wang <xiyou.wangcong@...il.com>
Cc:	David Miller <davem@...emloft.net>, paulmck@...ux.vnet.ibm.com,
	peterz@...radead.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: 2.6.34-rc1: rcu lockdep bug?

Le vendredi 12 mars 2010 à 16:59 +0800, Américo Wang a écrit :
> On Fri, Mar 12, 2010 at 4:07 PM, David Miller <davem@...emloft.net> wrote:
> > From: Américo Wang <xiyou.wangcong@...il.com>
> > Date: Fri, 12 Mar 2010 15:56:03 +0800
> >
> >> Ok, after decoding the lockdep output, it looks like that
> >> netif_receive_skb() should call rcu_read_lock_bh() instead of rcu_read_lock()?
> >> But I don't know if all callers of netif_receive_skb() are in softirq context.
> >
> > Normally, netif_receive_skb() is invoked from softirq context.
> >
> > However, via netpoll it can be invoked essentially from any context.
> >
> > But, when this happens, the networking receive path makes amends such
> > that this works fine.  That's what the netpoll_receive_skb() check in
> > netif_receive_skb() is for.  That check makes it bail out early if the
> > call to netif_receive_skb() is via a netpoll invocation.
> >
> 
> Oh, I see. This means we should call rcu_read_lock_bh() instead.
> If Paul has no objections, I will send a patch for this.
> 

Nope, its calling rcu_read_lock() from interrupt context and it should
stay as is (we dont need to disable bh, this has a cpu cost)



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/