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 Acked-by: John Stultz --- include/linux/clocksource.h | 3 +++ kernel/time/timekeeping.c | 9 +++++++-- 2 files changed, 10 insertions(+), 2 deletions(-) Index: linux-compile-i386.git/kernel/time/timekeeping.c =================================================================== --- linux-compile-i386.git.orig/kernel/time/timekeeping.c 2008-01-09 14:17:53.000000000 -0500 +++ linux-compile-i386.git/kernel/time/timekeeping.c 2008-01-09 15:17:30.000000000 -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 /** Index: linux-compile-i386.git/include/linux/clocksource.h =================================================================== --- linux-compile-i386.git.orig/include/linux/clocksource.h 2008-01-09 14:23:42.000000000 -0500 +++ linux-compile-i386.git/include/linux/clocksource.h 2008-01-09 15:17:30.000000000 -0500 @@ -274,6 +274,9 @@ 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); -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/