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authorjohn stultz <johnstul@us.ibm.com>2007-03-05 00:30:50 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-03-05 07:57:53 -0800
commit6bb74df481223731af6c7e0ff3adb31f6442cfcd (patch)
tree2aa0b0cfa55cb4b9a9236bd94b723d83eb0bdaa8 /kernel/time
parent4540768011352d38afb89d400eacb3e261507b70 (diff)
[PATCH] clocksource init adjustments (fix bug #7426)
This patch resolves the issue found here: http://bugme.osdl.org/show_bug.cgi?id=7426 The basic summary is: Currently we register most of i386/x86_64 clocksources at module_init time. Then we enable clocksource selection at late_initcall time. This causes some problems for drivers that use gettimeofday for init calibration routines (specifically the es1968 driver in this case), where durring module_init, the only clocksource available is the low-res jiffies clocksource. This may cause slight calibration errors, due to the small sampling time used. It should be noted that drivers that require fine grained time may not function on architectures that do not have better then jiffies resolution timekeeping (there are a few). However, this does not discount the reasonable need for such fine-grained timekeeping at init time. Thus the solution here is to register clocksources earlier (ideally when the hardware is being initialized), and then we enable clocksource selection at fs_initcall (before device_initcall). This patch should probably get some testing time in -mm, since clocksource selection is one of the most important issues for correct timekeeping, and I've only been able to test this on a few of my own boxes. Signed-off-by: John Stultz <johnstul@us.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: "David S. Miller" <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/clocksource.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 193a0793af9..5b0e46b56fd 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -55,16 +55,18 @@ static DEFINE_SPINLOCK(clocksource_lock);
static char override_name[32];
static int finished_booting;
-/* clocksource_done_booting - Called near the end of bootup
+/* clocksource_done_booting - Called near the end of core bootup
*
- * Hack to avoid lots of clocksource churn at boot time
+ * Hack to avoid lots of clocksource churn at boot time.
+ * We use fs_initcall because we want this to start before
+ * device_initcall but after subsys_initcall.
*/
static int __init clocksource_done_booting(void)
{
finished_booting = 1;
return 0;
}
-late_initcall(clocksource_done_booting);
+fs_initcall(clocksource_done_booting);
#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
static LIST_HEAD(watchdog_list);