linux-kernel - Re: [PATCH v3] powerpc/pseries: Fix cpu_hotplug_lock acquisition in resize

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Message-Id: <46DlGX5qJ5z9sNk@ozlabs.org>
Date:   Thu, 22 Aug 2019 23:08:52 +1000 (AEST)
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        Paul Mackerras <paulus@...ba.org>,
        Nicholas Piggin <npiggin@...il.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
Cc:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] powerpc/pseries: Fix cpu_hotplug_lock acquisition in resize_hpt()

On Wed, 2019-05-15 at 07:45:52 UTC, "Gautham R. Shenoy" wrote:
> From: "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
> 
> The calls to arch_add_memory()/arch_remove_memory() are always made
> with the read-side cpu_hotplug_lock acquired via
> memory_hotplug_begin().  On pSeries,
> arch_add_memory()/arch_remove_memory() eventually call resize_hpt()
> which in turn calls stop_machine() which acquires the read-side
> cpu_hotplug_lock again, thereby resulting in the recursive acquisition
> of this lock.
...
> 
> Fix this issue by
>   1) Requiring all the calls to pseries_lpar_resize_hpt() be made
>      with cpu_hotplug_lock held.
> 
>   2) In pseries_lpar_resize_hpt() invoke stop_machine_cpuslocked()
>      as a consequence of 1)
> 
>   3) To satisfy 1), in hpt_order_set(), call mmu_hash_ops.resize_hpt()
>      with cpu_hotplug_lock held.
> 
> Reported-by: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com>
> Signed-off-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/c784be435d5dae28d3b03db31753dd7a18733f0c

cheers