linux-kernel - [RESEND][PATCH] Fix oops on !GENERIC_TIME systems when accessing current

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Message-ID: <1267475683.4216.61.camel@localhost.localdomain>
Date:	Mon, 01 Mar 2010 12:34:43 -0800
From:	john stultz <johnstul@...ibm.com>
To:	greg kh <greg@...ah.com>, Ingo Molnar <mingo@...e.hu>,
	stable@...nel.org
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	aaro.koskinen@....fi, lkml <linux-kernel@...r.kernel.org>
Subject: [RESEND][PATCH] Fix oops on !GENERIC_TIME systems when accessing
 current_clocksource

No one has replied to this, so I wanted to send it out again.

Aaro Koskinen reported an issue in bug #15366, where on non-GENERIC_TIME
systems,
accessing /sys/devices/system/clocksource/clocksource0/current_clocksource would oops the system. 

It seems the timekeeper/clocksource rework missed initializing the
curr_clocksource value in the !GENERIC_TIME.

The following patch makes sure it gets initialized, and avoids the
issue.

Thanks to Aaro for reporting and diagnosing the issue as well as testing
the fix!

Bug Details: http://bugzilla.kernel.org/show_bug.cgi?id=15366

Too late for 2.6.33, but this likely should go into 2.6.33-stable and
2.6.32-stable.

thanks
-john

Signed-off-by: John Stultz <johnstul@...ibm.com>

diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index e85c234..c436ee5 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -568,6 +568,10 @@ static inline void clocksource_select(void) { }
  */
 static int __init clocksource_done_booting(void)
 {
+	mutex_lock(&clocksource_mutex);
+	curr_clocksource = clocksource_default_clock();
+	mutex_unlock(&clocksource_mutex);
+
 	finished_booting = 1;

 	/*

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