netdev - Re: [PATCH] use cond_resched() to replace udelay() when dump eeprom

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] [day] [month] [year] [list]

Message-ID: <1400046089.7000.27.camel@LTIRV-MCHAN1.corp.ad.broadcom.com>
Date:	Tue, 13 May 2014 22:41:29 -0700
From:	Michael Chan <mchan@...adcom.com>
To:	David Miller <davem@...emloft.net>
CC:	<acho@...e.com>, <netdev@...r.kernel.org>, <bpoirier@...e.de>
Subject: Re: [PATCH] use cond_resched() to replace udelay() when dump eeprom

On Wed, 2014-05-14 at 00:53 -0400, David Miller wrote: 
> From: Michael Chan <mchan@...adcom.com>
> Date: Mon, 12 May 2014 10:48:30 -0700
> 
> > We still need to time these commands.  Using cond_resched(), the timing
> > becomes unpredictable.  Perhaps we can reduce the NVRAM_CMD_TIMEOUT
> > counter by a factor of 100 and use msleep(1) instead of udelay(10).
> 
> That should work.

It actually won't work very well.  It typically takes 10 to 20 us to
read one 32-bit value.  Using msleep(1), it will take 100 times longer
than it should.  When dumping the entire NVRAM, it will visibly take a
very long time.

We are working on a patch to make sure that the clock is not running
slow when reading the NVRAM.  I think we can also reduce
NVRAM_CMD_TIMEOUT to something more reasonable.

--
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