lkml.org 
[lkml]   [2008]   [Jan]   [25]   [last100]   RSS Feed
Views: [more markup]  [less markup]  [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
DateFri, 25 Jan 2008 23:22:00 -0500
FromSteven Rostedt <>
Subject[PATCH 08/23 -v6] initialize the clock source to jiffies clock.
The latency tracer can call clocksource_read very early in bootup and
before the clock source variable has been initialized. This results in a
crash at boot up (even before earlyprintk is initialized). Since the
clock->read variable points to NULL.

This patch simply initializes the clock to use clocksource_jiffies, so
that any early user of clocksource_read will not crash.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: John Stultz <johnstul@us.ibm.com>
---
 include/linux/clocksource.h |    3 +++
 kernel/time/timekeeping.c   |    9 +++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)
Index: linux-mcount.git/include/linux/clocksource.h
===================================================================
--- linux-mcount.git.orig/include/linux/clocksource.h	2008-01-25 21:47:09.000000000 -0500
+++ linux-mcount.git/include/linux/clocksource.h	2008-01-25 21:47:11.000000000 -0500
@@ -273,6 +273,9 @@ extern struct clocksource* clocksource_g
 extern void clocksource_change_rating(struct clocksource *cs, int rating);
 extern void clocksource_resume(void);
 
+/* used to initialize clock */
+extern struct clocksource clocksource_jiffies;
+
 #ifdef CONFIG_GENERIC_TIME_VSYSCALL
 extern void update_vsyscall(struct timespec *ts, struct clocksource *c);
 extern void update_vsyscall_tz(void);
Index: linux-mcount.git/kernel/time/timekeeping.c
===================================================================
--- linux-mcount.git.orig/kernel/time/timekeeping.c	2008-01-25 21:47:09.000000000 -0500
+++ linux-mcount.git/kernel/time/timekeeping.c	2008-01-25 21:47:11.000000000 -0500
@@ -53,8 +53,13 @@ static inline void update_xtime_cache(u6
 	timespec_add_ns(&xtime_cache, nsec);
 }
 
-static struct clocksource *clock; /* pointer to current clocksource */
-
+/*
+ * pointer to current clocksource
+ *  Just in case we use clocksource_read before we initialize
+ *  the actual clock source. Instead of calling a NULL read pointer
+ *  we return jiffies.
+ */
+static struct clocksource *clock = &clocksource_jiffies;
 
 #ifdef CONFIG_GENERIC_TIME
 /**
-- 


\
 
 \ /
  Last update: 2008-01-26 05:35    [from the cache]
©2003-2008