From: Ingo Molnar <mingo@elte.hu>
To: Mike Travis <travis@sgi.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: tip/master merge problem?
Date: Fri, 2 Jan 2009 17:06:21 +0100 [thread overview]
Message-ID: <20090102160621.GE1180@elte.hu> (raw)
In-Reply-To: <495BED6D.8040307@sgi.com>
* Mike Travis <travis@sgi.com> wrote:
>
> Hi Ingo,
>
> I found this code snippet in kernel/sched.c in the tip/master tree. It
> appears to be a merge mistake: (cut and pasted - no tabs)
>
> 292 /*
> 293 * If this cpu is the one which updates jiffies, then
> 294 * give up the assignment and let it be taken by the
> 295 * cpu which runs the tick timer next, which might be
> 296 * this cpu as well. If we don't drop this here the
> 297 * jiffies might be stale and do_timer() never
> 298 * invoked.
> 299 */
> 300 if (cpu == tick_do_timer_cpu)
> 301 tick_do_timer_cpu = TICK_DO_TIMER_NONE;
> 302
> 303 if (delta_jiffies > 1)
> 304
> 305 /* Skip reprogram of event if its not changed */
> 306 if (ts->tick_stopped && ktime_equal(expires, dev->next_event))
> 307 goto out;
> 308
> 309 cpumask_set_cpu(cpu, nohz_cpu_mask);
>
> I think the "Skip reprogram" was inserted into the middle of a previous
> if-then statement.
indeed, this is plain broken. It happened to build and boot but still it's
broken.
> git blames it on:
> 00147449 (Woodruff, Richard 2008-12-01 14:18:11 -0800 292) /*
> 00147449 (Woodruff, Richard 2008-12-01 14:18:11 -0800 293) * If this cpu is the one which updates jiffies, then
> 00147449 (Woodruff, Richard 2008-12-01 14:18:11 -0800 294) * give up the assignment and let it be taken by the
> 00147449 (Woodruff, Richard 2008-12-01 14:18:11 -0800 295) * cpu which runs the tick timer next, which might be
> 00147449 (Woodruff, Richard 2008-12-01 14:18:11 -0800 296) * this cpu as well. If we don't drop this here the
> 00147449 (Woodruff, Richard 2008-12-01 14:18:11 -0800 297) * jiffies might be stale and do_timer() never
> 00147449 (Woodruff, Richard 2008-12-01 14:18:11 -0800 298) * invoked.
> 00147449 (Woodruff, Richard 2008-12-01 14:18:11 -0800 299) */
> 00147449 (Woodruff, Richard 2008-12-01 14:18:11 -0800 300) if (cpu == tick_do_timer_cpu)
> 00147449 (Woodruff, Richard 2008-12-01 14:18:11 -0800 301) tick_do_timer_cpu = TICK_DO_TIMER_NONE;
> 00147449 (Woodruff, Richard 2008-12-01 14:18:11 -0800 302)
> 6ba9b346 (Ingo Molnar 2007-02-19 18:11:56 +0000 303) if (delta_jiffies > 1)
> 00147449 (Woodruff, Richard 2008-12-01 14:18:11 -0800 304)
> 00147449 (Woodruff, Richard 2008-12-01 14:18:11 -0800 305) /* Skip reprogram of event if its not changed */
> 00147449 (Woodruff, Richard 2008-12-01 14:18:11 -0800 306) if (ts->tick_stopped && ktime_equal(expires, dev->next_event))
> 00147449 (Woodruff, Richard 2008-12-01 14:18:11 -0800 307) goto out;
> 00147449 (Woodruff, Richard 2008-12-01 14:18:11 -0800 308)
> 6a7b3dc3 (Rusty Russell 2008-11-25 02:35:04 +1030 309) cpumask_set_cpu(cpu, nohz_cpu_mask);
>
> I've Cc'd both interested parties.
purely my fault. I've zapped that conflict resolution and picked up yours.
Ingo
prev parent reply other threads:[~2009-01-02 16:06 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-31 22:08 tip/master merge problem? Mike Travis
2009-01-02 16:06 ` Ingo Molnar [this message]
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