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Re: [Xen-devel] Sixth (and final?) release candidate for Xen 3.4.3

To: "Langsdorf, Mark" <mark.langsdorf@xxxxxxx>
Subject: Re: [Xen-devel] Sixth (and final?) release candidate for Xen 3.4.3
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Wed, 12 May 2010 20:21:20 +0100
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On 12/05/2010 18:50, "Langsdorf, Mark" <mark.langsdorf@xxxxxxx> wrote:

> Sometimes, on the new 6-core processors, the powernow.c
> driver call:
>     on_selected_cpus(&cmd.mask, transition_pstate, &cmd, 0);

Since you specify '0' for the final 'wait' parameter of on_selected_cpus(),
the call can return before transition_pstate() has finished executing on all
the requested CPUs. Hence the calling function (powernow_cpufreq_target) can
exit early, and 'cmd' becomes invalid as it is allocated in the function's
stack frame.

The fix is simply to specify '1' for the final parameter of
on_selected_cpus(). I will apply the fix to all trees and also have a quick
audit that all other callers who specify '0' really mean to.

 -- Keir

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