linux-kernel - Re: [PATCH] psi: avoid divide-by-zero crash inside virtual machines

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Message-Id: <20190214115855.76869aecd777fbd37d48f45c@linux-foundation.org>
Date:   Thu, 14 Feb 2019 11:58:55 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Johannes Weiner <hannes@...xchg.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Łukasz Siudut <lsiudut@...com>,
        linux-kernel@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH] psi: avoid divide-by-zero crash inside virtual machines

On Thu, 14 Feb 2019 14:31:57 -0500 Johannes Weiner <hannes@...xchg.org> wrote:

> --- a/kernel/sched/psi.c
> +++ b/kernel/sched/psi.c
> @@ -322,7 +322,7 @@ static bool update_stats(struct psi_group *group)
>  	expires = group->next_update;
>  	if (now < expires)
>  		goto out;
> -	if (now - expires > psi_period)
> +	if (now - expires >= psi_period)
>  		missed_periods = div_u64(now - expires, psi_period);
>  
>  	/*

It seems appropriate to use time_after64() and friends in this code.