linux-kernel - Re: [PATCH] sched: make p->prio independent of p->mm

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Message-ID: <20200424084339.189d4ee6@gandalf.local.home>
Date:   Fri, 24 Apr 2020 08:43:39 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Hillf Danton <hdanton@...a.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Mike Galbraith <efault@....de>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] sched: make p->prio independent of p->mm

On Fri, 24 Apr 2020 10:12:31 +0800
Hillf Danton <hdanton@...a.com> wrote:

> Yes and if you agree, we send it home during the 5.8 cycle, or not before
> fifo is reclaimed from modules.
> 
> In the spin it now looks like
> 
> --- a/include/linux/sched/prio.h
> +++ b/include/linux/sched/prio.h
> @@ -12,15 +12,12 @@
>   * tasks are in the range MAX_RT_PRIO..MAX_PRIO-1. Priority
>   * values are inverted: lower p->prio value means higher priority.
>   *
> - * The MAX_USER_RT_PRIO value allows the actual maximum
> - * RT priority to be separate from the value exported to
> - * user-space.  This allows kernel threads to set their
> - * priority to a value higher than any user task. Note:
> - * MAX_RT_PRIO must not be smaller than MAX_USER_RT_PRIO.
> + * Note: MAX_USER_RT_PRIO will be removed as early as 5.8,
> + * don't use it in new code.
>   */
>  
> -#define MAX_USER_RT_PRIO	100
> -#define MAX_RT_PRIO		MAX_USER_RT_PRIO
> +#define MAX_RT_PRIO		100
> +#define MAX_USER_RT_PRIO	MAX_RT_PRIO
>  
>  #define MAX_PRIO		(MAX_RT_PRIO + NICE_WIDTH)
>  #define DEFAULT_PRIO		(MAX_RT_PRIO + NICE_WIDTH / 2)

No one has used it in years, I don't think we need this change. Just delete
it in one go.

Is making p->prio independent from p->mm needed for other changes? If not,
then we can hold off this change until we do so, otherwise, I would keep
your original patch as is, and then remove the extra check when we remove
MAX_USER_RT_PRIO.

-- Steve