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Subject: Re: 2.6.15-rc5-rt2 won't boot on dual 933
From: Steven Rostedt <rostedt@goodmis.org>
To: "K.R. Foley" <kr@cybsft.com>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel <linux-kernel@vger.kernel.org>
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Date: Sun, 18 Dec 2005 19:51:13 -0500
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On Sun, 2005-12-18 at 15:55 -0600, K.R. Foley wrote:
> dump_stack+0x1e/0x20 (20)
>  [<c011c9df>] preempt_enable_no_resched+0x5f/0x70 (20)
>  [<c0100ff2>] cpu_idle+0xb2/0x100 (40)
>  [<c0111446>] start_secondary+0x296/0x340<6> 

Ingo,

What's the reason for this printing out in cpu_idle?

#ifdef CONFIG_DEBUG_PREEMPT
void notrace preempt_enable_no_resched(void)
{
	static int once = 1;

	barrier();
	dec_preempt_count();

	if (once && !preempt_count()) {
		once = 0;
		printk(KERN_ERR "BUG: %s:%d task might have lost a preemption check!
\n",
			current->comm, current->pid);
		dump_stack();
	}
}

EXPORT_SYMBOL(preempt_enable_no_resched);
#endif

I can understand the above when using preempt_enable_no_resched, when
you know that you still have preemption on, but sometimes (as in
cpu_idle) it is used just before calling schedule.  So this check is
pretty much meaningless.

---

KR, 

Does your kernel boot without CONFIG_DEBUG_PREEMPT?

-- Steve


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