Re: [PATCH 7/8] sched/isolation: Fix housekeeping_mask memory leak

From: "Paul E. McKenney" <paulmck@kernel.org>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	LKML <linux-kernel@vger.kernel.org>, Tejun Heo <tj@kernel.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Alex Belits <abelits@marvell.com>, Nitesh Lal <nilal@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Nicolas Saenz <nsaenzju@redhat.com>,
	Christoph Lameter <cl@gentwo.de>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Zefan Li <lizefan.x@bytedance.com>,
	Paul Gortmaker <paul.gortmaker@windriver.com>
Subject: Re: [PATCH 7/8] sched/isolation: Fix housekeeping_mask memory leak
Date: Wed, 5 Jan 2022 15:30:34 -0800	[thread overview]
Message-ID: <20220105233034.GA977207@paulmck-ThinkPad-P17-Gen-1> (raw)
In-Reply-To: <20220104144944.1278663-8-frederic@kernel.org>

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@kernel.org>

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

> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Juri Lelli <juri.lelli@redhat.com>
> Cc: Marcelo Tosatti <mtosatti@redhat.com>
> Cc: Nitesh Lal <nilal@redhat.com>
> Cc: Nicolas Saenz <nsaenzju@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Christoph Lameter <cl@gentwo.de>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Zefan Li <lizefan.x@bytedance.com>
> Cc: Alex Belits <abelits@marvell.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
> 