linux-kernel - Re: [PATCH] x86/resctrl: Ensure usage of CPUs are locked while needed

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Date:   Mon, 10 Dec 2018 21:49:15 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Reinette Chatre <reinette.chatre@...el.com>
Cc:     tglx@...utronix.de, fenghua.yu@...el.com, tony.luck@...el.com,
        jithu.joseph@...el.com, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] x86/resctrl: Ensure usage of CPUs are locked while needed

On Wed, Nov 28, 2018 at 10:22:07AM -0800, Reinette Chatre wrote:
> The user triggers the creation of a pseudo-locked region when writing
> the requested schemata to the schemata resctrl file. The pseudo-locking
> of a region is required to be done on a CPU that is associated with the
> cache on which the pseudo-locked region will reside. In order to run the
> locking code on a specific CPU the needed CPU has to be selected and
> ensured to remain online during the entire locking sequence.
> 
> At this time the cpu_hotplug_lock is not taken during the pseudo-lock
> region creation and it is thus possible for a CPU to be selected to run
> the pseudo-locking code and then that CPU to go offline before the
> thread is able to run on it.
> 
> Fix this by ensuring that the cpu_hotplug_lock is taken while the CPU on
> which code has to run needs to be controlled. Since the cpu_hotplug_lock
> is always taken before rdtgroup_mutex the lock order is maintained.
> 
> Fixes: e0bdfe8e36f3 ("x86/intel_rdt: Support creation/removal of pseudo-locked region")
> Signed-off-by: Reinette Chatre <reinette.chatre@...el.com>
> Cc: stable@...r.kernel.org
> ---
>  arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 4 ++++
>  1 file changed, 4 insertions(+)

This looks like it wants to go in now, right?

If so, pls redo this patch against tip/x86/urgent which has the old
filenames, before the resctrl rename and reorg.

Thx.

-- 
Regards/Gruss,
    Boris.

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