linux-kernel - Re: [PATCH v7 02/24] x86/resctrl: kfree() rmid_ptrs from rdtgroup

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Date:   Thu, 9 Nov 2023 09:39:44 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     James Morse <james.morse@....com>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Fenghua Yu <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Babu Moger <Babu.Moger@....com>,
        <shameerali.kolothum.thodi@...wei.com>,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        <carl@...amperecomputing.com>, <lcherian@...vell.com>,
        <bobo.shaobowang@...wei.com>, <tan.shaopeng@...itsu.com>,
        <baolin.wang@...ux.alibaba.com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Xin Hao <xhao@...ux.alibaba.com>, <peternewman@...gle.com>,
        <dfustini@...libre.com>, <amitsinght@...vell.com>
Subject: Re: [PATCH v7 02/24] x86/resctrl: kfree() rmid_ptrs from
 rdtgroup_exit()

Hi James,

Subject refers to rdtgroup_exit() but the patch is actually changing
resctrl_exit().

On 10/25/2023 11:03 AM, 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_exit_mon_l3_config() to cleanup any memory allocated
> by rdt_get_mon_l3_config().

To match what patch actually does it looks like this should rather be:
"Add resctrl_exit_mon_l3_config()" -> "Add resctrl_put_mon_l3_config()" 

> 
> There is no reason to backport this to a stable kernel.
> 
> Signed-off-by: James Morse <james.morse@....com>
> ---
> Changes since v5:
>  * This patch is new
> 
> Changes since v6:
>  * Removed struct rdt_resource argument, added __exit markers to match the
>    only caller.
>  * Adedd a whole stack of functions to maintain symmetry.
> ---
>  arch/x86/kernel/cpu/resctrl/core.c     |  6 ++++++
>  arch/x86/kernel/cpu/resctrl/internal.h |  1 +
>  arch/x86/kernel/cpu/resctrl/monitor.c  | 15 +++++++++++++++
>  3 files changed, 22 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 19e0681f0435..0056c9962a44 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -992,7 +992,13 @@ late_initcall(resctrl_late_init);
>  
>  static void __exit resctrl_exit(void)
>  {
> +	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
> +
>  	cpuhp_remove_state(rdt_online);
> +
> +	if (r->mon_capable)
> +		rdt_put_mon_l3_config(r);
> +
>  	rdtgroup_exit();
>  }

I expect cleanup to do the inverse of init. I do not know what was the
motivation for the rdtgroup_exit() to follow cpuhp_remove_state() but I
was expecting this new cleanup to be done after rdtgroup_exit() to be inverse
of init. This cleanup is inserted in middle of two existing cleanup - could
you please elaborate how this location was chosen?

Reinette