linux-kernel - Re: [PATCH] x86/intel_rdt: use __this_cpu_read in pseudo_lock

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Message-ID: <ddb942f0-4c34-4e10-7d46-526d411f5ebd@intel.com>
Date:   Tue, 27 Jul 2021 11:56:04 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Hui Su <suhui@...u.com>, <fenghua.yu@...el.com>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
        <x86@...nel.org>, <hpa@...or.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/intel_rdt: use __this_cpu_read in pseudo_lock_fn()

Hi,

On 7/22/2021 7:33 PM, Hui Su wrote:
> The code is executed with interrupts disabled,
> so it's safe to use __this_cpu_read().

True ... but could you please elaborate what the issue is with using 
this_cpu_read()? It too is safe to use when interrupts are disabled.

> 
> Signed-off-by: Hui Su <suhui@...u.com>
> ---
>   arch/x86/kernel/cpu/resctrl/pseudo_lock.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
> index 2207916cae65..f0cc0a89333b 100644
> --- a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
> +++ b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
> @@ -464,8 +464,8 @@ static int pseudo_lock_fn(void *_rdtgrp)
>   	 * cache.
>   	 */
>   	__wrmsr(MSR_MISC_FEATURE_CONTROL, prefetch_disable_bits, 0x0);
> -	closid_p = this_cpu_read(pqr_state.cur_closid);
> -	rmid_p = this_cpu_read(pqr_state.cur_rmid);
> +	closid_p = __this_cpu_read(pqr_state.cur_closid);
> +	rmid_p = __this_cpu_read(pqr_state.cur_rmid);
>   	mem_r = plr->kmem;
>   	size = plr->size;
>   	line_size = plr->line_size;
> 

Reinette