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Date: Thu, 10 Oct 2013 10:34:26 +0800
From: Xishi Qiu <qiuxishi@huawei.com>
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To: LKML <linux-kernel@vger.kernel.org>
Subject: kdump: kdump can't boot in this case
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I write a module, and find kdump can't boot in this case.
kernel version is 3.12, Intel(R) Xeon(R) CPU	E5620

struct timer_list g_timer;

void tmrhnd_invtssfault(unsigned long data)
{
	long __res;
	printk(KERN_EMERG "invalid TSS fault in interrupt context.\n");
	__asm__ volatile("int $0x0A" : "=a"(__res):);
}

{
	...
	init_timer(&g_timer);
	g_timer.expires = jiffies + 10;
	g_timer.data = 0;
	g_timer.function = tmrhnd_invtssfault;
	add_timer(&g_timer);
	...
}

If access NULL pointer instead of "__asm__ volatile("int $0x0A" : "=a"(__res):);" 
in tmrhnd_invtssfault(), kdump can boot.
And if not use timer, just do "__asm__ volatile("int $0x0A" : "=a"(__res):);" only
once in module, kdump can boot too.