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

[Paul E. McKenney]

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@xxxxxxxxxx>

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

> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
> Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
> Cc: Nitesh Lal <nilal@xxxxxxxxxx>
> Cc: Nicolas Saenz <nsaenzju@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Christoph Lameter <cl@xxxxxxxxx>
> Cc: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Zefan Li <lizefan.x@xxxxxxxxxxxxx>
> Cc: Alex Belits <abelits@xxxxxxxxxxx>
> ---
>  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
>