Re: [PATCH] chrt: when more than one argument, interpret first argument as priority

Benno Schulenberg <[email protected]> Fri, 27 Jun 2025 13:32:32 +0200

Newsgroups	org.kernel.vger.util-linux
Message-ID	<[email protected]>

Op 27-06-2025 om 10:38 schreef Madadi Vineeth Reddy:
> On 26/06/25 16:57, Benno Schulenberg wrote:
>> The first argument is a priority not only for `chrt --pid <prio> <pid>`
>> but also for `chrt <prio> <command> [<argument>...]`.
> 
> Good catch. SCHED_RR is indeed taken by default when no policy is given.
> 
> We could address this by initializing `need_prio` to `true` by default,
> and then setting it to `false` in the corresponding switch cases for
> policies that don't require a priority.

Well, that change is redundant with my proposed change.

Also, setting 'need_prio' to true by default gives a somewhat wrong
impression, because no priority is needed when only option --pid is
given.

What your proposed change accomplishes is that the error message
for the mistaken `./chrt somecommand` changes from:

   chrt: unsupported priority value for the policy: 0: see --max for valid range

to:

   chrt: bad usage
   Try 'chrt --help' for more information.

I think both error messages are equally poor -- the first is puzzling,
the second too unspecific.  It would be better to combine your change
with more specific feedback, depending on whether --pid was given.  I'll
send a better patch next week.

Benno

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