Re: [PATCH 2.6.21-rc5] Flush MSI-X table writes (rev 3)
From: Andrew Morton
Date: Fri Mar 30 2007 - 15:48:15 EST
On Fri, 30 Mar 2007 13:04:02 -0600
ebiederm@xxxxxxxxxxxx (Eric W. Biederman) wrote:
> Mitch Williams <mitch.a.williams@xxxxxxxxx> writes:
> > 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.
> Acked-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Did we end up deciding whether this is (needed*safe) enough for 2.6.21?
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