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Date: Sun, 25 Mar 2007 10:06:26 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Roland Dreier <rdreier@cisco.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Early hang with 2.6.21-rc4-rt1
Message-ID: <20070325080626.GA22223@elte.hu>
References: <adad52xnccs.fsf@cisco.com> <ada8xdlnb6f.fsf@cisco.com> <20070325072947.GA10734@elte.hu> <20070325073424.GA14242@elte.hu>
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* Ingo Molnar <mingo@elte.hu> wrote:

> hm - on 32-bit, CRITICAL_IRQSOFF_TIMING+FUNCTION_TRACING works fine 
> for me. I'll try the 64-bit kernel too.

the 64-bit kernel indeed hangs. Does the patch below fix it for you?

	Ingo

Index: linux/kernel/timer.c
===================================================================
--- linux.orig/kernel/timer.c
+++ linux/kernel/timer.c
@@ -822,8 +822,23 @@ EXPORT_SYMBOL(xtime);
 /* XXX - all of this timekeeping code should be later moved to time.c */
 #include <linux/clocksource.h>
 
+/*
+ * Dummy clocksource just in case someone tries to use the
+ * clocksource infrastructure before timekeeping_init() is
+ * called:
+ */
+static notrace cycle_t read_boot(void)
+{
+	return 0;
+}
+
+static __initdata struct clocksource clocksource_boot = {
+	.name			= "boot",
+	.read			= read_boot,
+};
+
 /* pointer to current clocksource: */
-static __read_mostly struct clocksource *clock;
+static __read_mostly struct clocksource *clock = &clocksource_boot;
 
 #ifdef CONFIG_GENERIC_TIME
 /**