linux-kernel - Re: [PATCH 1/3] PCI: vpd handle longer delays in access

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Date:	Mon, 8 Sep 2008 13:40:25 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	jbarnes@...tuousgeek.org, bhutchings@...arflare.com,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] PCI: vpd handle longer delays in access

On Thu, 04 Sep 2008 13:56:37 -0700
Stephen Hemminger <shemminger@...tta.com> wrote:

> Accessing the VPD area can take a long time.  The existing 
> VPD access code fails consistently on my hardware. There are comments
> in the SysKonnect vendor driver that it can take up to 13ms per word. 
> 
> Change the access routines to:
>   * use a mutex rather than spinning with IRQ's disabled and lock held
>   * have a longer timeout
>   * call schedule while spinning to provide some responsivness

It doesn't call schedule() - it calls yield().

yield() is pretty notoriously badly behaved in the presence of lots of
runnable tasks and there's been a general move to eradicate its
in-kernel callsites.

An alternative would be nice.

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