linux-kernel - Re: [RFC][PATCH 02/11] sched: SCHED

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1271182937.4807.1879.camel@twins>
Date:	Tue, 13 Apr 2010 20:22:17 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Raistlin <raistlin@...ux.it>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Chris Friesen <cfriesen@...tel.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Darren Hart <darren@...art.com>,
	Henrik Austad <henrik@...tad.us>,
	Johan Eker <johan.eker@...csson.com>,
	"p.faure" <p.faure@...tech.ch>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Claudio Scordino <claudio@...dence.eu.com>,
	michael trimarchi <trimarchi@...is.sssup.it>,
	Fabio Checconi <fabio@...dalf.sssup.it>,
	Tommaso Cucinotta <t.cucinotta@...up.it>,
	Juri Lelli <juri.lelli@...il.com>,
	Nicola Manica <nicola.manica@...il.com>,
	Luca Abeni <luca.abeni@...tn.it>
Subject: Re: [RFC][PATCH 02/11] sched: SCHED_DEADLINE policy implementation.

On Sun, 2010-02-28 at 20:17 +0100, Raistlin wrote:
> +/*
> + * Here we check if --at time t-- a task (which is probably being
> + * [re]activated or, in general, enqueued) can use its remaining runtime
> + * and its current deadline _without_ exceeding the bandwidth it is
> + * assigned (function returns true if it can).
> + *
> + * For this to hold, we must check if:
> + *   runtime / (deadline - t) < dl_runtime / dl_deadline .
> + */
> +static bool dl_check_bandwidth(struct sched_dl_entity *dl_se, u64 t)
> +{
> +       u64 left, right;
> +
> +       /*
> +        * left and right are the two sides of the equation above,
> +        * after a bit of shuffling to use multiplications instead
> +        * of divisions.
> +        */
> +       left = dl_se->dl_deadline * dl_se->runtime;
> +       right = (dl_se->deadline - t) * dl_se->dl_runtime;
> +
> +       return dl_time_before(left, right);
> +} 

So what happens when we overflow u64?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/