linux-kernel - Re: [PATCH 29/30] Documentation: tracing: add TIF_NEED_RESCHED

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Date: Wed, 21 Feb 2024 18:53:24 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Ankur Arora <ankur.a.arora@...cle.com>
Cc: linux-kernel@...r.kernel.org, tglx@...utronix.de, peterz@...radead.org,
 torvalds@...ux-foundation.org, paulmck@...nel.org,
 akpm@...ux-foundation.org, luto@...nel.org, bp@...en8.de,
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 Masami Hiramatsu <mhiramat@...nel.org>, Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH 29/30] Documentation: tracing: add TIF_NEED_RESCHED_LAZY

On Wed, 21 Feb 2024 15:22:20 -0800
Ankur Arora <ankur.a.arora@...cle.com> wrote:


> > I wonder if we should also add this information in /sys/kernel/tracing/README
> > so that it is easier to find on a machine.  
> 
> Yeah, there is a problem with the discovery. Seems a little out of place
> in tracing/README though.
> 
> How about something like this? Though this isn't really a model of clarity.

Could work, but I would also have it check the configs that are set in the
kernel, and only show the options that are available with the current
configs that are enabled in the kernel.

> 
>     --- a/kernel/trace/trace.c
>     +++ b/kernel/trace/trace.c
>     @@ -4292,7 +4292,7 @@ static void print_lat_help_header(struct seq_file *m)
>     {
>             seq_puts(m, "#                    _------=> CPU#            \n"
>                     "#                   / _-----=> irqs-off/BH-disabled\n"
>     -                   "#                  | / _----=> need-resched    \n"
>     +                   "#                  | / _----=> need-resched  [ l: lazy, n: now, p: preempt, b: l|n, L: l|p, N: n|p, B: l|n|p ]\n"
>                     "#                  || / _---=> hardirq/softirq \n"
>                     "#                  ||| / _--=> preempt-depth   \n"
>                     "#                  |||| / _-=> migrate-disable \n"
> 
> 
> Also, haven't looked at trace-cmd. Anything I should be sending a patch
> out for?

There's really nothing that explains it. But that probably should be fixed.

-- Steve