Messages in this thread Patch in this message | | | Date | Wed, 23 Jan 2008 11:02:44 -0500 | From | Steven Rostedt <> | Subject | [PATCH 08/20 -v5] initialize the clock source to jiffies clock. |
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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 2008-01-23 10:26:57.000000000 -0500 +++ linux-mcount.git/include/linux/clocksource.h 2008-01-23 10:27:04.000000000 -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 2008-01-23 10:26:57.000000000 -0500 +++ linux-mcount.git/kernel/time/timekeeping.c 2008-01-23 10:27:04.000000000 -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 /** --
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