netdev - Re: [PATCH] ixgbe: Introduce new 10GbE driver for Intel 82598 based PCI Express adapters...

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: <468D7EBD.7020103@garzik.org>
Date:	Thu, 05 Jul 2007 19:29:01 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Inaky Perez-Gonzalez <inaky@...ux.intel.com>
CC:	"Kok, Auke" <auke-jan.h.kok@...el.com>,
	Michael Buesch <mb@...sch.de>,
	Christoph Hellwig <hch@...radead.org>,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	"Veeraiyan, Ayyappan" <ayyappan.veeraiyan@...el.com>,
	netdev@...r.kernel.org, arjan@...ux.intel.com,
	akpm@...ux-foundation.org
Subject: Re: [PATCH] ixgbe: Introduce new 10GbE driver for Intel 82598 based
 PCI Express adapters...

Inaky Perez-Gonzalez wrote:
> On Tuesday 03 July 2007, Jeff Garzik wrote:
>> Inaky Perez-Gonzalez wrote:
>> Access to bitfields are not atomic within the machine int in which they 
>> are stored... you need to "unpack" the values stored in bitfields, even 
>> if they are single-bit bitfields.
> 
> Which we do manually when we don't use bitfields. Again, conceptually,
> there is no difference.

Practically speaking -- there are differences.

The "manual" method hides nothing from the programmer, while use of 
bitfields hides the lack of atomicity.

When you have programmers who make mistakes -- i.e. real humans -- these 
things matter.

But overall, it is not any one detail that discourages use of bitfields; 
it is the sum of all the reasons.  Practical experience, compiler 
technology, mistakes made (and not made), all point to avoiding bitfields.

	Jeff


-
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