From 8107d8296baff899db89c1716fe8af69a5b19d18 Mon Sep 17 00:00:00 2001 From: Christian Borntraeger Date: Thu, 27 Nov 2008 11:05:56 +0100 Subject: [PATCH] [S390] fix/cleanup sched_clock CONFIG_PRINTK_TIME reveals that sched_clock has a wrong offset during boot: .. [ 0.000000] Movable zone: 0 pages used for memmap [ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 775679 [ 0.000000] Kernel command line: dasd=4b6c root=/dev/dasda1 ro noinitrd [ 0.000000] PID hash table entries: 4096 (order: 12, 32768 bytes) [6920575.975232] console [ttyS0] enabled [6920575.987586] Dentry cache hash table entries: 524288 (order: 10, 4194304 bytes) [6920575.991404] Inode-cache hash table entries: 262144 (order: 9, 2097152 bytes) .. The s390 implementation of sched_clock uses the store clock instruction and subtracts jiffies_timer_cc. jiffies_timer_cc is a local variable in arch/s390/kernel/time.c and only used for sched_clock and monotonic clock. For historical reasons there is an offset on that value. With todays code this offset is unnecessary. By removing that offset we can get a sched_clock which returns the nanoseconds after time_init. This improves CONFIG_PRINTK_TIME. Since sched_clock is the only user, I have also renamed jiffies_timer_cc to sched_clock_base_cc. In addition, the local variable init_timer_cc is redundant and can be romved as well. Signed-off-by: Christian Borntraeger Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/time.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c index b94e9e3b694..eccefbbff88 100644 --- a/arch/s390/kernel/time.c +++ b/arch/s390/kernel/time.c @@ -59,7 +59,7 @@ static ext_int_info_t ext_int_info_cc; static ext_int_info_t ext_int_etr_cc; -static u64 jiffies_timer_cc; +static u64 sched_clock_base_cc; static DEFINE_PER_CPU(struct clock_event_device, comparators); @@ -68,7 +68,7 @@ static DEFINE_PER_CPU(struct clock_event_device, comparators); */ unsigned long long sched_clock(void) { - return ((get_clock_xt() - jiffies_timer_cc) * 125) >> 9; + return ((get_clock_xt() - sched_clock_base_cc) * 125) >> 9; } /* @@ -229,13 +229,10 @@ static struct clocksource clocksource_tod = { */ void __init time_init(void) { - u64 init_timer_cc; - - init_timer_cc = reset_tod_clock(); - jiffies_timer_cc = init_timer_cc - jiffies_64 * CLK_TICKS_PER_JIFFY; + sched_clock_base_cc = reset_tod_clock(); /* set xtime */ - tod_to_timeval(init_timer_cc - TOD_UNIX_EPOCH, &xtime); + tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, &xtime); set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec); @@ -289,7 +286,7 @@ static unsigned long long adjust_time(unsigned long long old, delta = -delta; adjust.offset = -ticks * (1000000 / HZ); } - jiffies_timer_cc += delta; + sched_clock_base_cc += delta; if (adjust.offset != 0) { printk(KERN_NOTICE "etr: time adjusted by %li micro-seconds\n", adjust.offset); -- 2.41.0