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Date: Tue, 29 Sep 2009 20:15:37 +0200
Message-ID: <25e057c00909291115t63c36ddm657f9359d1ae34f4@mail.gmail.com>
Subject: Re: [RFC][PATCH] SCHED_EDF scheduling class
From: roel kluin <roel.kluin@gmail.com>
To: Raistlin <raistlin@linux.it>
Cc: Linus Walleij <linus.ml.walleij@gmail.com>,
       Peter Zijlstra <peterz@infradead.org>, claudio@evidence.eu.com,
       michael@evidence.eu.com, mingo@elte.hu, linux-kernel@vger.kernel.org,
       tglx@linutronix.de, johan.eker@ericsson.com, p.faure@akatech.ch,
       Fabio Checconi <fabio@gandalf.sssup.it>,
       Dhaval Giani <dhaval.giani@gmail.com>,
       Steven Rostedt <rostedt@goodmis.org>,
       Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
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Lines: 37

> ?static int __sched_setscheduler(struct task_struct *p, int policy,
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? struct sched_param *param, bool user)
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? struct sched_param *param,
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? struct sched_param_ex *param_ex,
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? bool user)
...

> @@ -6200,6 +6364,13 @@ recheck:
> ? ? ? ? ? ?(p->mm && param->sched_priority > MAX_USER_RT_PRIO-1) ||
> ? ? ? ? ? ?(!p->mm && param->sched_priority > MAX_RT_PRIO-1))
> ? ? ? ? ? ? ? ?return -EINVAL;
> + ? ? ? if (edf_policy(policy) && param_ex->sched_priority != 0)
> + ? ? ? ? ? ? ? return -EINVAL;
> + ? ? ? if (edf_policy(policy) && (param_ex == NULL ||
> + ? ? ? ? ? timespec_to_ns(&param_ex->sched_period) == 0 ||
> + ? ? ? ? ? timespec_to_ns(&param_ex->sched_period) <
> + ? ? ? ? ? timespec_to_ns(&param_ex->sched_runtime)))
> + ? ? ? ? ? ? ? return -EINVAL;

shouldn't the NULL test be moved upwards, to prevent a dereference of
a NULL pointer? 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;
        }

Roel
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