[PATCH] ppc64: fix initialisation of gettimeofday calculations

On PPC64, we keep track of when we need to update jiffies (and the
variables used to calculate the time of day) based on the time base.

If the time base frequence is sufficiently high compared to the
processor clock frequency, then it is possible for the time of day
variables to be corrupted at the time of the first decrementer interrupt
we take.  This became obvious on a legacy iSeries where the time base
frequency is the same as the processor clock.

This one line patch fixes the initialisation so that the time of day
variables and the indicator we use to tell when updates are due are
better synchronised.

Signed-off-by:  Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/ppc64/kernel/time.c b/arch/ppc64/kernel/time.c
index 772a465..3d54745 100644 (file)
--- a/arch/ppc64/kernel/time.c
+++ b/arch/ppc64/kernel/time.c
@@ -515,6 +515,7 @@ void __init time_init(void)
        do_gtod.varp = &do_gtod.vars[0];
        do_gtod.var_idx = 0;
        do_gtod.varp->tb_orig_stamp = tb_last_stamp;
+       get_paca()->next_jiffy_update_tb = tb_last_stamp + tb_ticks_per_jiffy;
        do_gtod.varp->stamp_xsec = xtime.tv_sec * XSEC_PER_SEC;
        do_gtod.tb_ticks_per_sec = tb_ticks_per_sec;
        do_gtod.varp->tb_to_xs = tb_to_xs;