netdev - Re: [PATCH] macvlan: lockless tx path

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: <1289423555.17691.8.camel@edumazet-laptop>
Date:	Wed, 10 Nov 2010 22:12:35 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
Cc:	Ben Greear <greearb@...delatech.com>,
	David Miller <davem@...emloft.net>,
	Patrick McHardy <kaber@...sh.net>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] macvlan: lockless tx path

Le mercredi 10 novembre 2010 à 21:04 +0000, Ben Hutchings a écrit :

> Drivers should calculate differences and accumulate them in a 64-bit
> counter.  (A lot of hardware has read-to-clear counters anyway, in which
> case the driver *has* to accumulate the values it reads.)

You are mistaken. These are _hardware_ counters. If they were software,
of course they would be 32 or 64 bit.

And doing the thing you describe in software is racy.
I tried to remove many races, not to add new ones.

Yes, some drivers read one hardware counter using two instructions, and
this is racy.



--
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