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Message-ID: <52f81c45-efa7-42c7-86f4-fc1084b1d57a@redhat.com>
Date: Tue, 20 Feb 2024 16:27:45 +0100
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Subject: Re: [PATCH v9 02/24] x86/resctrl: kfree() rmid_ptrs from
 resctrl_exit()
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To: James Morse <james.morse@arm.com>, x86@kernel.org,
 linux-kernel@vger.kernel.org
Cc: Fenghua Yu <fenghua.yu@intel.com>,
 Reinette Chatre <reinette.chatre@intel.com>,
 Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
 Borislav Petkov <bp@alien8.de>, H Peter Anvin <hpa@zytor.com>,
 Babu Moger <Babu.Moger@amd.com>, shameerali.kolothum.thodi@huawei.com,
 D Scott Phillips OS <scott@os.amperecomputing.com>,
 carl@os.amperecomputing.com, lcherian@marvell.com,
 bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com,
 baolin.wang@linux.alibaba.com, Jamie Iles <quic_jiles@quicinc.com>,
 Xin Hao <xhao@linux.alibaba.com>, peternewman@google.com,
 dfustini@baylibre.com, amitsinght@marvell.com
References: <20240213184438.16675-1-james.morse@arm.com>
 <20240213184438.16675-3-james.morse@arm.com>
From: David Hildenbrand <david@redhat.com>
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In-Reply-To: <20240213184438.16675-3-james.morse@arm.com>
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On 13.02.24 19:44, James Morse wrote:
> rmid_ptrs[] is allocated from dom_data_init() but never free()d.
> 
> While the exit text ends up in the linker script's DISCARD section,
> the direction of travel is for resctrl to be/have loadable modules.
> 
> Add resctrl_put_mon_l3_config() to cleanup any memory allocated
> by rdt_get_mon_l3_config().
> 
> There is no reason to backport this to a stable kernel.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> Tested-by: Babu Moger <babu.moger@amd.com>
> Tested-by: Carl Worth <carl@os.amperecomputing.com> # arm64
> Reviewed-by: Babu Moger <babu.moger@amd.com>
> ---

[...]


> +static void __exit dom_data_exit(void)
> +{
> +	mutex_lock(&rdtgroup_mutex);
> +
> +	kfree(rmid_ptrs);
> +	rmid_ptrs = NULL;
> +
> +	mutex_unlock(&rdtgroup_mutex);

Just curious: is grabbing that mutex really required?

Against which race are we trying to protect ourselves?

I suspect this mutex is not required here: if we could racing with 
someone else, likely freeing that memory would not be safe either.

Apart from that LGTM.

-- 
Cheers,

David / dhildenb