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Message-ID: <20090822171540.1220f50d@skybase>
Date: Sat, 22 Aug 2009 17:15:40 +0200
From: Martin Schwidefsky <schwidefsky@...ibm.com>
To: Ingo Molnar <mingo@...e.hu>
Cc: dwalker@...o99.com, mingo@...hat.com, hpa@...or.com,
linux-kernel@...r.kernel.org, johnstul@...ibm.com,
tglx@...utronix.de, linux-tip-commits@...r.kernel.org
Subject: Re: [tip:timers/core] timekeeping: Increase granularity of
read_persistent_clock()
On Sat, 22 Aug 2009 12:32:52 +0200
Ingo Molnar <mingo@...e.hu> wrote:
>
> * tip-bot for Martin Schwidefsky <schwidefsky@...ibm.com> wrote:
>
> > Commit-ID: d4f587c67fc39e0030ddd718675e252e208da4d7
> > Gitweb: http://git.kernel.org/tip/d4f587c67fc39e0030ddd718675e252e208da4d7
> > Author: Martin Schwidefsky <schwidefsky@...ibm.com>
> > AuthorDate: Fri, 14 Aug 2009 15:47:31 +0200
> > Committer: Thomas Gleixner <tglx@...utronix.de>
> > CommitDate: Sat, 15 Aug 2009 10:55:46 +0200
> >
> > timekeeping: Increase granularity of read_persistent_clock()
>
> FYI, -tip arch-testing found that this commit broke the PowerPC
> build:
>
> /home/mingo/tip/arch/powerpc/kernel/time.c: In function 'read_persistent_clock':
> /home/mingo/tip/arch/powerpc/kernel/time.c:788: error: 'return' with a value, in function returning void
> /home/mingo/tip/arch/powerpc/kernel/time.c:791: error: 'return' with a value, in function returning void
> make[2]: *** [arch/powerpc/kernel/time.o] Error 1
> make[2]: *** Waiting for unfinished jobs....
> make[1]: *** [arch/powerpc/kernel] Error 2
I overlooked a case in the powerpc version of read_persistent_lock.
New patch:
--
Subject: [PATCH] read_persistent_clock should return a timespec
From: Martin Schwidefsky <schwidefsky@...ibm.com>
The persistent clock of some architectures (e.g. s390) have a
better granularity than seconds. To reduce the delta between the
host clock and the guest clock in a virtualized system change the
read_persistent_clock function to return a struct timespec.
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: john stultz <johnstul@...ibm.com>
Cc: Daniel Walker <dwalker@...o99.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
---
arch/m68knommu/kernel/time.c | 5 +--
arch/mips/dec/time.c | 5 +--
arch/mips/lasat/ds1603.c | 5 +--
arch/mips/lasat/sysctl.c | 8 +++--
arch/mips/lemote/lm2e/setup.c | 5 +--
arch/mips/mti-malta/malta-time.c | 5 +--
arch/mips/pmc-sierra/yosemite/setup.c | 5 +--
arch/mips/sibyte/swarm/setup.c | 15 +++++++--
arch/mips/sni/time.c | 5 +--
arch/powerpc/kernel/time.c | 14 +++++----
arch/s390/kernel/time.c | 22 ++------------
arch/sh/kernel/time.c | 6 +--
arch/x86/kernel/rtc.c | 5 +--
arch/xtensa/kernel/time.c | 5 +--
include/linux/time.h | 2 -
kernel/time/timekeeping.c | 52 ++++++++++++++++++----------------
16 files changed, 88 insertions(+), 76 deletions(-)
Index: linux-2.6/arch/m68knommu/kernel/time.c
===================================================================
--- linux-2.6.orig/arch/m68knommu/kernel/time.c
+++ linux-2.6/arch/m68knommu/kernel/time.c
@@ -72,9 +72,10 @@ static unsigned long read_rtc_mmss(void)
return mktime(year, mon, day, hour, min, sec);;
}
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
{
- return read_rtc_mmss();
+ ts->tv_sec = read_rtc_mmss();
+ ts->tv_nsec = 0;
}
int update_persistent_clock(struct timespec now)
Index: linux-2.6/arch/mips/dec/time.c
===================================================================
--- linux-2.6.orig/arch/mips/dec/time.c
+++ linux-2.6/arch/mips/dec/time.c
@@ -18,7 +18,7 @@
#include <asm/dec/ioasic.h>
#include <asm/dec/machtype.h>
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
{
unsigned int year, mon, day, hour, min, sec, real_year;
unsigned long flags;
@@ -53,7 +53,8 @@ unsigned long read_persistent_clock(void
year += real_year - 72 + 2000;
- return mktime(year, mon, day, hour, min, sec);
+ ts->tv_sec = mktime(year, mon, day, hour, min, sec);
+ ts->tv_nsec = 0;
}
/*
Index: linux-2.6/arch/mips/lasat/ds1603.c
===================================================================
--- linux-2.6.orig/arch/mips/lasat/ds1603.c
+++ linux-2.6/arch/mips/lasat/ds1603.c
@@ -135,7 +135,7 @@ static void rtc_end_op(void)
lasat_ndelay(1000);
}
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
{
unsigned long word;
unsigned long flags;
@@ -147,7 +147,8 @@ unsigned long read_persistent_clock(void
rtc_end_op();
spin_unlock_irqrestore(&rtc_lock, flags);
- return word;
+ ts->tv_sec = word;
+ ts->tv_nsec = 0;
}
int rtc_mips_set_mmss(unsigned long time)
Index: linux-2.6/arch/mips/lasat/sysctl.c
===================================================================
--- linux-2.6.orig/arch/mips/lasat/sysctl.c
+++ linux-2.6/arch/mips/lasat/sysctl.c
@@ -92,10 +92,12 @@ static int rtctmp;
int proc_dolasatrtc(ctl_table *table, int write, struct file *filp,
void *buffer, size_t *lenp, loff_t *ppos)
{
+ struct timespec ts;
int r;
if (!write) {
- rtctmp = read_persistent_clock();
+ read_persistent_clock(&ts);
+ rtctmp = ts.tv_sec;
/* check for time < 0 and set to 0 */
if (rtctmp < 0)
rtctmp = 0;
@@ -134,9 +136,11 @@ int sysctl_lasat_rtc(ctl_table *table,
void *oldval, size_t *oldlenp,
void *newval, size_t newlen)
{
+ struct timespec ts;
int r;
- rtctmp = read_persistent_clock();
+ read_persistent_clock(&ts);
+ rtctmp = ts.tv_sec;
if (rtctmp < 0)
rtctmp = 0;
r = sysctl_intvec(table, oldval, oldlenp, newval, newlen);
Index: linux-2.6/arch/mips/lemote/lm2e/setup.c
===================================================================
--- linux-2.6.orig/arch/mips/lemote/lm2e/setup.c
+++ linux-2.6/arch/mips/lemote/lm2e/setup.c
@@ -54,9 +54,10 @@ void __init plat_time_init(void)
mips_hpt_frequency = cpu_clock_freq / 2;
}
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
{
- return mc146818_get_cmos_time();
+ ts->tv_sec = mc146818_get_cmos_time();
+ ts->tv_nsec = 0;
}
void (*__wbflush)(void);
Index: linux-2.6/arch/mips/mti-malta/malta-time.c
===================================================================
--- linux-2.6.orig/arch/mips/mti-malta/malta-time.c
+++ linux-2.6/arch/mips/mti-malta/malta-time.c
@@ -100,9 +100,10 @@ static unsigned int __init estimate_cpu_
return count;
}
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
{
- return mc146818_get_cmos_time();
+ ts->tv_sec = mc146818_get_cmos_time();
+ ts->tv_nsec = 0;
}
static void __init plat_perf_setup(void)
Index: linux-2.6/arch/mips/pmc-sierra/yosemite/setup.c
===================================================================
--- linux-2.6.orig/arch/mips/pmc-sierra/yosemite/setup.c
+++ linux-2.6/arch/mips/pmc-sierra/yosemite/setup.c
@@ -70,7 +70,7 @@ void __init bus_error_init(void)
}
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
{
unsigned int year, month, day, hour, min, sec;
unsigned long flags;
@@ -92,7 +92,8 @@ unsigned long read_persistent_clock(void
m48t37_base->control = 0x00;
spin_unlock_irqrestore(&rtc_lock, flags);
- return mktime(year, month, day, hour, min, sec);
+ ts->tv_sec = mktime(year, month, day, hour, min, sec);
+ ts->tv_nsec = 0;
}
int rtc_mips_set_time(unsigned long tim)
Index: linux-2.6/arch/mips/sibyte/swarm/setup.c
===================================================================
--- linux-2.6.orig/arch/mips/sibyte/swarm/setup.c
+++ linux-2.6/arch/mips/sibyte/swarm/setup.c
@@ -87,19 +87,26 @@ enum swarm_rtc_type {
enum swarm_rtc_type swarm_rtc_type;
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
{
+ unsigned long sec;
+
switch (swarm_rtc_type) {
case RTC_XICOR:
- return xicor_get_time();
+ sec = xicor_get_time();
+ break;
case RTC_M4LT81:
- return m41t81_get_time();
+ sec = m41t81_get_time();
+ break;
case RTC_NONE:
default:
- return mktime(2000, 1, 1, 0, 0, 0);
+ sec = mktime(2000, 1, 1, 0, 0, 0);
+ break;
}
+ ts->tv_sec = sec;
+ tv->tv_nsec = 0;
}
int rtc_mips_set_time(unsigned long sec)
Index: linux-2.6/arch/mips/sni/time.c
===================================================================
--- linux-2.6.orig/arch/mips/sni/time.c
+++ linux-2.6/arch/mips/sni/time.c
@@ -182,7 +182,8 @@ void __init plat_time_init(void)
setup_pit_timer();
}
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
{
- return -1;
+ ts->tv_sec = -1;
+ ts->tv_nsec = 0;
}
Index: linux-2.6/arch/powerpc/kernel/time.c
===================================================================
--- linux-2.6.orig/arch/powerpc/kernel/time.c
+++ linux-2.6/arch/powerpc/kernel/time.c
@@ -772,7 +772,7 @@ int update_persistent_clock(struct times
return ppc_md.set_rtc_time(&tm);
}
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
{
struct rtc_time tm;
static int first = 1;
@@ -787,11 +787,15 @@ unsigned long read_persistent_clock(void
if (ppc_md.get_boot_time)
return ppc_md.get_boot_time() -timezone_offset;
}
- if (!ppc_md.get_rtc_time)
- return 0;
+ if (!ppc_md.get_rtc_time) {
+ ts->tv_sec = 0;
+ ts->tv_nsec = 0;
+ return;
+ }
ppc_md.get_rtc_time(&tm);
- return mktime(tm.tm_year+1900, tm.tm_mon+1, tm.tm_mday,
- tm.tm_hour, tm.tm_min, tm.tm_sec);
+ ts->tv_sec = mktime(tm.tm_year+1900, tm.tm_mon+1, tm.tm_mday,
+ tm.tm_hour, tm.tm_min, tm.tm_sec);
+ ts->tv_nsec = 0;
}
/* clocksource code */
Index: linux-2.6/arch/s390/kernel/time.c
===================================================================
--- linux-2.6.orig/arch/s390/kernel/time.c
+++ linux-2.6/arch/s390/kernel/time.c
@@ -182,12 +182,9 @@ static void timing_alert_interrupt(__u16
static void etr_reset(void);
static void stp_reset(void);
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
{
- struct timespec ts;
-
- tod_to_timeval(get_clock() - TOD_UNIX_EPOCH, &ts);
- return ts.tv_sec;
+ tod_to_timeval(get_clock() - TOD_UNIX_EPOCH, ts);
}
static cycle_t read_tod_clock(struct clocksource *cs)
@@ -248,7 +245,6 @@ void __init time_init(void)
{
struct timespec ts;
unsigned long flags;
- cycle_t now;
/* Reset time synchronization interfaces. */
etr_reset();
@@ -266,20 +262,10 @@ void __init time_init(void)
panic("Could not register TOD clock source");
/*
- * The TOD clock is an accurate clock. The xtime should be
- * initialized in a way that the difference between TOD and
- * xtime is reasonably small. Too bad that timekeeping_init
- * sets xtime.tv_nsec to zero. In addition the clock source
- * change from the jiffies clock source to the TOD clock
- * source add another error of up to 1/HZ second. The same
- * function sets wall_to_monotonic to a value that is too
- * small for /proc/uptime to be accurate.
- * Reset xtime and wall_to_monotonic to sane values.
+ * Reset wall_to_monotonic to the initial timestamp created
+ * in head.S to get a precise value in /proc/uptime.
*/
write_seqlock_irqsave(&xtime_lock, flags);
- now = get_clock();
- tod_to_timeval(now - TOD_UNIX_EPOCH, &xtime);
- clocksource_tod.cycle_last = now;
tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, &ts);
set_normalized_timespec(&wall_to_monotonic, -ts.tv_sec, -ts.tv_nsec);
write_sequnlock_irqrestore(&xtime_lock, flags);
Index: linux-2.6/arch/sh/kernel/time.c
===================================================================
--- linux-2.6.orig/arch/sh/kernel/time.c
+++ linux-2.6/arch/sh/kernel/time.c
@@ -39,11 +39,9 @@ void (*rtc_sh_get_time)(struct timespec
int (*rtc_sh_set_time)(const time_t) = null_rtc_set_time;
#ifdef CONFIG_GENERIC_CMOS_UPDATE
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
{
- struct timespec tv;
- rtc_sh_get_time(&tv);
- return tv.tv_sec;
+ rtc_sh_get_time(&ts);
}
int update_persistent_clock(struct timespec now)
Index: linux-2.6/arch/x86/kernel/rtc.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/rtc.c
+++ linux-2.6/arch/x86/kernel/rtc.c
@@ -178,7 +178,7 @@ static int set_rtc_mmss(unsigned long no
}
/* not static: needed by APM */
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
{
unsigned long retval, flags;
@@ -186,7 +186,8 @@ unsigned long read_persistent_clock(void
retval = get_wallclock();
spin_unlock_irqrestore(&rtc_lock, flags);
- return retval;
+ ts->tv_sec = retval;
+ ts->tv_nsec = 0;
}
int update_persistent_clock(struct timespec now)
Index: linux-2.6/arch/xtensa/kernel/time.c
===================================================================
--- linux-2.6.orig/arch/xtensa/kernel/time.c
+++ linux-2.6/arch/xtensa/kernel/time.c
@@ -59,9 +59,8 @@ static struct irqaction timer_irqaction
void __init time_init(void)
{
- xtime.tv_nsec = 0;
- xtime.tv_sec = read_persistent_clock();
-
+ /* FIXME: xtime&wall_to_monotonic are set in timekeeping_init. */
+ read_persistent_clock(&xtime);
set_normalized_timespec(&wall_to_monotonic,
-xtime.tv_sec, -xtime.tv_nsec);
Index: linux-2.6/include/linux/time.h
===================================================================
--- linux-2.6.orig/include/linux/time.h
+++ linux-2.6/include/linux/time.h
@@ -101,7 +101,7 @@ extern struct timespec xtime;
extern struct timespec wall_to_monotonic;
extern seqlock_t xtime_lock;
-extern unsigned long read_persistent_clock(void);
+extern void read_persistent_clock(struct timespec *ts);
extern int update_persistent_clock(struct timespec now);
extern int no_sync_cmos_clock __read_mostly;
void timekeeping_init(void);
Index: linux-2.6/kernel/time/timekeeping.c
===================================================================
--- linux-2.6.orig/kernel/time/timekeeping.c
+++ linux-2.6/kernel/time/timekeeping.c
@@ -154,7 +154,7 @@ __cacheline_aligned_in_smp DEFINE_SEQLOC
*/
struct timespec xtime __attribute__ ((aligned (16)));
struct timespec wall_to_monotonic __attribute__ ((aligned (16)));
-static unsigned long total_sleep_time; /* seconds */
+static struct timespec total_sleep_time;
/*
* The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock.
@@ -487,17 +487,18 @@ int timekeeping_valid_for_hres(void)
}
/**
- * read_persistent_clock - Return time in seconds from the persistent clock.
+ * read_persistent_clock - Return time from the persistent clock.
*
* Weak dummy function for arches that do not yet support it.
- * Returns seconds from epoch using the battery backed persistent clock.
- * Returns zero if unsupported.
+ * Reads the time from the battery backed persistent clock.
+ * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
*
* XXX - Do be sure to remove it once all arches implement it.
*/
-unsigned long __attribute__((weak)) read_persistent_clock(void)
+void __attribute__((weak)) read_persistent_clock(struct timespec *ts)
{
- return 0;
+ ts->tv_sec = 0;
+ ts->tv_nsec = 0;
}
/*
@@ -507,7 +508,9 @@ void __init timekeeping_init(void)
{
struct clocksource *clock;
unsigned long flags;
- unsigned long sec = read_persistent_clock();
+ struct timespec now;
+
+ read_persistent_clock(&now);
write_seqlock_irqsave(&xtime_lock, flags);
@@ -518,19 +521,20 @@ void __init timekeeping_init(void)
clock->enable(clock);
timekeeper_setup_internals(clock);
- xtime.tv_sec = sec;
- xtime.tv_nsec = 0;
+ xtime.tv_sec = now.tv_sec;
+ xtime.tv_nsec = now.tv_nsec;
raw_time.tv_sec = 0;
raw_time.tv_nsec = 0;
set_normalized_timespec(&wall_to_monotonic,
-xtime.tv_sec, -xtime.tv_nsec);
update_xtime_cache(0);
- total_sleep_time = 0;
+ total_sleep_time.tv_sec = 0;
+ total_sleep_time.tv_nsec = 0;
write_sequnlock_irqrestore(&xtime_lock, flags);
}
/* time in seconds when suspend began */
-static unsigned long timekeeping_suspend_time;
+static struct timespec timekeeping_suspend_time;
/**
* timekeeping_resume - Resumes the generic timekeeping subsystem.
@@ -543,18 +547,19 @@ static unsigned long timekeeping_suspend
static int timekeeping_resume(struct sys_device *dev)
{
unsigned long flags;
- unsigned long now = read_persistent_clock();
+ struct timespec ts;
+
+ read_persistent_clock(&ts);
clocksource_resume();
write_seqlock_irqsave(&xtime_lock, flags);
- if (now && (now > timekeeping_suspend_time)) {
- unsigned long sleep_length = now - timekeeping_suspend_time;
-
- xtime.tv_sec += sleep_length;
- wall_to_monotonic.tv_sec -= sleep_length;
- total_sleep_time += sleep_length;
+ if (timespec_compare(&ts, &timekeeping_suspend_time) > 0) {
+ ts = timespec_sub(ts, timekeeping_suspend_time);
+ xtime = timespec_add_safe(xtime, ts);
+ wall_to_monotonic = timespec_sub(wall_to_monotonic, ts);
+ total_sleep_time = timespec_add_safe(total_sleep_time, ts);
}
update_xtime_cache(0);
/* re-base the last cycle value */
@@ -577,7 +582,7 @@ static int timekeeping_suspend(struct sy
{
unsigned long flags;
- timekeeping_suspend_time = read_persistent_clock();
+ read_persistent_clock(&timekeeping_suspend_time);
write_seqlock_irqsave(&xtime_lock, flags);
timekeeping_forward_now();
@@ -800,9 +805,10 @@ void update_wall_time(void)
*/
void getboottime(struct timespec *ts)
{
- set_normalized_timespec(ts,
- - (wall_to_monotonic.tv_sec + total_sleep_time),
- - wall_to_monotonic.tv_nsec);
+ struct timespec boottime;
+
+ boottime = timespec_add_safe(wall_to_monotonic, total_sleep_time);
+ set_normalized_timespec(ts, -boottime.tv_sec, -boottime.tv_nsec);
}
/**
@@ -811,7 +817,7 @@ void getboottime(struct timespec *ts)
*/
void monotonic_to_bootbased(struct timespec *ts)
{
- ts->tv_sec += total_sleep_time;
+ *ts = timespec_add_safe(*ts, total_sleep_time);
}
unsigned long get_seconds(void)
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
--
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