linux-kernel - Re: [PATCH 2.6.20.4] Flush MSI-X table writes (rev 3)

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Date:	Fri, 30 Mar 2007 12:09:51 -0700
From:	Greg KH <gregkh@...e.de>
To:	Mitch Williams <mitch.a.williams@...el.com>
Cc:	linux-pci@...ey.karlin.mff.cuni.cz, ebiederm@...ssion.com,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	auke-jan.h.kok@...el.com
Subject: Re: [PATCH 2.6.20.4] Flush MSI-X table writes (rev 3)

On Fri, Mar 30, 2007 at 12:03:47PM -0700, Mitch Williams wrote:
> This patch fixes a kernel bug which is triggered when using the
> irqbalance daemon with MSI-X hardware.
> 
> Because both MSI-X interrupt messages and MSI-X table writes are posted,
> it's possible for them to cross while in-flight.  This results in
> interrupts being received long after the kernel thinks they're disabled,
> and in interrupts being sent to stale vectors after rebalancing.
> 
> This patch performs a read flush after writes to the MSI-X table for
> mask and unmask operations.  Since the SMP affinity is set while
> the interrupt is masked, and since it's unmasked immediately after,
> no additional flushes are required in the various affinity setting
> routines.
> 
> This patch has been validated with (unreleased) network hardware which
> uses MSI-X.
> 
> Revised with input from Eric Biederman.
> 
> Signed-off-by: Mitch Williams <mitch.a.williams@...el.com>

Sorry, but this isn't going to go into 2.6.20 any time soon as it
doesn't fit the rules for the -stable tree.

But I'll take an updated version for my pci tree to go to Linus after
2.6.21 is out.

thanks,

greg k-h
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