netdev - Re: e1000_netpoll(): disable_irq() triggers might

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: <alpine.DEB.2.11.1410292201530.5308@nanos>
Date:	Wed, 29 Oct 2014 22:03:20 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Sabrina Dubroca <sd@...asysnail.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, jeffrey.t.kirsher@...el.com
Subject: Re: e1000_netpoll(): disable_irq() triggers might_sleep() on
 linux-next

On Wed, 29 Oct 2014, Peter Zijlstra wrote:

> On Wed, Oct 29, 2014 at 09:23:42PM +0100, Thomas Gleixner wrote:
> > But at least it allows to mitigate the impact by making it conditional
> > at a central point.
> > 
> > static inline void netpoll_lock(struct net_device *nd)
> > {
> > 	if (netpoll_active(nd))
> > 		spin_lock(&nd->netpoll_lock);
> > }
> 
> branch fail vs lock might be a toss on most machines, but if we're
> hitting cold cachelines we loose big.

Well, if the net_device is not cache hot on irq entry you have lost
already. The extra branch/lock is not going to add much to that.
 
Thanks,

	tglx
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html