linux-kernel - Re: [RFC][PATCH] SCHED

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Message-Id: <1254326342.11233.149.camel@Palantir>
Date:	Wed, 30 Sep 2009 17:59:02 +0200
From:	Raistlin <raistlin@...ux.it>
To:	roel kluin <roel.kluin@...il.com>
Cc:	Linus Walleij <linus.ml.walleij@...il.com>,
	Peter Zijlstra <peterz@...radead.org>, claudio@...dence.eu.com,
	michael@...dence.eu.com, mingo@...e.hu,
	linux-kernel@...r.kernel.org, tglx@...utronix.de,
	johan.eker@...csson.com, p.faure@...tech.ch,
	Fabio Checconi <fabio@...dalf.sssup.it>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Tommaso Cucinotta <tommaso.cucinotta@...up.it>
Subject: Re: [RFC][PATCH] SCHED_EDF scheduling class

On Tue, 2009-09-29 at 20:15 +0200, roel kluin wrote:
> shouldn't the NULL test be moved upwards, to prevent a dereference of
> a NULL pointer? 
I definitely think you _do_ are right, many thanks! :-P

> Also I notice that `timespec_to_ns(&param_ex->sched_period)'
> is called twice, maybe gcc does this but can't we do something like
> 
>         if (edf_policy(policy)) {
>                 if (param_ex == NULL || param_ex->sched_priority != 0)
>                         return -EINVAL;
>                 s64 psp = timespec_to_ns(&param_ex->sched_period);
>                 if (psp == 0 || psp < timespec_to_ns(&param_ex->sched_runtime))
>                         return -EINVAL;
>         }
> 
Well, don't know... I guess the compiler do _something_ (also since
timespec_to_ns is 'static inline') but, to be sincere, I've not looked
at the assembly yet... But I may check it out, at least for x86, and
then consider this. :)

Thanks very much for your comments and suggestions,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
----------------------------------------------------------------------
Dario Faggioli, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa  (Italy)

http://blog.linux.it/raistlin / raistlin@...ga.net /
dario.faggioli@...ber.org

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