linux-kernel - Re: [PATCH 7/8] sched/isolation: Fix housekeeping

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Message-ID: <20220105233034.GA977207@paulmck-ThinkPad-P17-Gen-1>
Date:   Wed, 5 Jan 2022 15:30:34 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>, Tejun Heo <tj@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Alex Belits <abelits@...vell.com>,
        Nitesh Lal <nilal@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Nicolas Saenz <nsaenzju@...hat.com>,
        Christoph Lameter <cl@...two.de>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Zefan Li <lizefan.x@...edance.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: Re: [PATCH 7/8] sched/isolation: Fix housekeeping_mask memory leak

On Tue, Jan 04, 2022 at 03:49:43PM +0100, Frederic Weisbecker wrote:
> If "nohz_full=" or "isolcpus=nohz" are called with CONFIG_NO_HZ_FULL=n,
> housekeeping_mask doesn't get freed despite it being unused if
> housekeeping_setup() is called for the first time.
> 
> Check this scenario first to fix this, so that no useless allocation
> is performed.
> 
> Signed-off-by: Frederic Weisbecker <frederic@...nel.org>

Reviewed-by: Paul E. McKenney <paulmck@...nel.org>

> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Juri Lelli <juri.lelli@...hat.com>
> Cc: Marcelo Tosatti <mtosatti@...hat.com>
> Cc: Nitesh Lal <nilal@...hat.com>
> Cc: Nicolas Saenz <nsaenzju@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Christoph Lameter <cl@...two.de>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Zefan Li <lizefan.x@...edance.com>
> Cc: Alex Belits <abelits@...vell.com>
> ---
>  kernel/sched/isolation.c | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
> index 828dacec483e..883eee9fae22 100644
> --- a/kernel/sched/isolation.c
> +++ b/kernel/sched/isolation.c
> @@ -94,6 +94,14 @@ static int __init housekeeping_setup(char *str, enum hk_flags flags)
>  	cpumask_var_t non_housekeeping_mask, housekeeping_staging;
>  	int err = 0;
>  
> +	if ((flags & HK_FLAG_TICK) && !(housekeeping_flags & HK_FLAG_TICK)) {
> +		if (!IS_ENABLED(CONFIG_NO_HZ_FULL)) {
> +			pr_warn("Housekeeping: nohz unsupported."
> +				" Build with CONFIG_NO_HZ_FULL\n");
> +			return 0;
> +		}
> +	}
> +
>  	alloc_bootmem_cpumask_var(&non_housekeeping_mask);
>  	if (cpulist_parse(str, non_housekeeping_mask) < 0) {
>  		pr_warn("Housekeeping: nohz_full= or isolcpus= incorrect CPU range\n");
> @@ -123,15 +131,8 @@ static int __init housekeeping_setup(char *str, enum hk_flags flags)
>  		}
>  	}
>  
> -	if ((flags & HK_FLAG_TICK) && !(housekeeping_flags & HK_FLAG_TICK)) {
> -		if (IS_ENABLED(CONFIG_NO_HZ_FULL)) {
> -			tick_nohz_full_setup(non_housekeeping_mask);
> -		} else {
> -			pr_warn("Housekeeping: nohz unsupported."
> -				" Build with CONFIG_NO_HZ_FULL\n");
> -			goto free_housekeeping_staging;
> -		}
> -	}
> +	if ((flags & HK_FLAG_TICK) && !(housekeeping_flags & HK_FLAG_TICK))
> +		tick_nohz_full_setup(non_housekeeping_mask);
>  
>  	housekeeping_flags |= flags;
>  	err = 1;
> -- 
> 2.25.1
>