netdev - Re: Kernel WARNING: at net/core/dev.c:1330 __netif

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: <200807242106.52672.nickpiggin@yahoo.com.au>
Date:	Thu, 24 Jul 2008 21:06:51 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	peterz@...radead.org, davem@...emloft.net, jarkao2@...il.com,
	Larry.Finger@...inger.net, kaber@...sh.net,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-wireless@...r.kernel.org, mingo@...hat.com,
	paulmck@...ux.vnet.ibm.com
Subject: Re: Kernel WARNING: at net/core/dev.c:1330 __netif_schedule+0x2c/0x98()

On Thursday 24 July 2008 20:55, Miklos Szeredi wrote:
> On Thu, 24 Jul 2008, Nick Piggin wrote:
> > Hey, something kind of cool (and OT) I've just thought of that we can
> > do with ticket locks is to take tickets for 2 (or 64K) nested locks,
> > and then wait for them both (all), so the cost is N*lock + longest spin,
> > rather than N*lock + N*avg spin.
>
> Isn't this deadlocky?
>
> E.g. one task takes ticket x=1, then other task comes in and takes x=2
> and y=1, then first task takes y=2.  Then neither can actually
> complete both locks.

Oh duh of course you still need mutual exclusion from the first lock
to order the subsequent :P

So yeah it only works for N > 2 locks, and you have to spin_lock the
first one... so unsuitable for scheduler.
--
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