[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <1243515570.6600.96.camel@laptop>
Date: Thu, 28 May 2009 14:59:30 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Paul Mundt <lethal@...ux-sh.org>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Daniel Walker <dwalker@...o99.com>,
Linus Walleij <linus.ml.walleij@...il.com>,
Ingo Molnar <mingo@...e.hu>,
Andrew Victor <linux@...im.org.za>,
Haavard Skinnemoen <hskinnemoen@...el.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, linux-sh@...r.kernel.org,
linux-arm-kernel@...ts.arm.linux.org.uk,
John Stultz <johnstul@...ux.vnet.ibm.com>
Subject: Re: [PATCH] sched: Support current clocksource handling in
fallback sched_clock().
On Thu, 2009-05-28 at 21:42 +0900, Paul Mundt wrote:
> unsigned long long __attribute__((weak)) sched_clock(void)
> {
> - return (unsigned long long)(jiffies - INITIAL_JIFFIES)
> - * (NSEC_PER_SEC / HZ);
> + struct clocksource *clock = ACCESS_ONCE(sched_clocksource);
> +
> + return cyc2ns(clock, clocksource_read(clock));
> }
>
> @@ -440,7 +444,17 @@ void clocksource_unregister(struct clocksource *cs)
> list_del(&cs->list);
> if (clocksource_override == cs)
> clocksource_override = NULL;
> +
> next_clocksource = select_clocksource();
> +
> + /*
> + * If select_clocksource() fails to find another suitable
> + * clocksource for sched_clocksource and we are unregistering
> + * it, switch back to jiffies.
> + */
> + if (sched_clocksource == cs)
> + sched_clocksource = &clocksource_jiffies;
> +
> spin_unlock_irqrestore(&clocksource_lock, flags);
> }
CPU0 CPU1
clock = ACCESS_ONCE(sched_clocksource);
unload module
clocksource_unregister()
sched_clocksource = jiffies
unmap data/text
cyc2ns(clock, clocksource_read(clock)) <--- fireworks
--
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/
Powered by blists - more mailing lists