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    Subject[tip:timers/core] timekeeping: Increase granularity of read_persistent_clock()
    Commit-ID:  d4f587c67fc39e0030ddd718675e252e208da4d7
    Gitweb: http://git.kernel.org/tip/d4f587c67fc39e0030ddd718675e252e208da4d7
    Author: Martin Schwidefsky <schwidefsky@de.ibm.com>
    AuthorDate: Fri, 14 Aug 2009 15:47:31 +0200
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitDate: Sat, 15 Aug 2009 10:55:46 +0200

    timekeeping: Increase granularity of read_persistent_clock()

    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.

    Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Acked-by: John Stultz <johnstul@us.ibm.com>
    Cc: Daniel Walker <dwalker@fifo99.com>
    LKML-Reference: <20090814134811.013873340@de.ibm.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>


    ---
    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 | 7 ++--
    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, 83 insertions(+), 74 deletions(-)

    diff --git a/arch/m68knommu/kernel/time.c b/arch/m68knommu/kernel/time.c
    index d182b2f..6843224 100644
    --- a/arch/m68knommu/kernel/time.c
    +++ b/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)
    diff --git a/arch/mips/dec/time.c b/arch/mips/dec/time.c
    index 463136e..02f505f 100644
    --- a/arch/mips/dec/time.c
    +++ b/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;
    }

    /*
    diff --git a/arch/mips/lasat/ds1603.c b/arch/mips/lasat/ds1603.c
    index 52cb143..c6fd96f 100644
    --- a/arch/mips/lasat/ds1603.c
    +++ b/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)
    diff --git a/arch/mips/lasat/sysctl.c b/arch/mips/lasat/sysctl.c
    index 8f88886..3f04d4c 100644
    --- a/arch/mips/lasat/sysctl.c
    +++ b/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);
    diff --git a/arch/mips/lemote/lm2e/setup.c b/arch/mips/lemote/lm2e/setup.c
    index ebd6cea..24b355d 100644
    --- a/arch/mips/lemote/lm2e/setup.c
    +++ b/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);
    diff --git a/arch/mips/mti-malta/malta-time.c b/arch/mips/mti-malta/malta-time.c
    index 0b97d47..3c6f190 100644
    --- a/arch/mips/mti-malta/malta-time.c
    +++ b/arch/mips/mti-malta/malta-time.c
    @@ -100,9 +100,10 @@ static unsigned int __init estimate_cpu_frequency(void)
    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)
    diff --git a/arch/mips/pmc-sierra/yosemite/setup.c b/arch/mips/pmc-sierra/yosemite/setup.c
    index 2d3c0dc..3498ac9 100644
    --- a/arch/mips/pmc-sierra/yosemite/setup.c
    +++ b/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)
    diff --git a/arch/mips/sibyte/swarm/setup.c b/arch/mips/sibyte/swarm/setup.c
    index 672e45d..623ffc9 100644
    --- a/arch/mips/sibyte/swarm/setup.c
    +++ b/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)
    diff --git a/arch/mips/sni/time.c b/arch/mips/sni/time.c
    index 0d9ec1a..62df6a5 100644
    --- a/arch/mips/sni/time.c
    +++ b/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;
    }
    diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
    index eae4511..ad63f30 100644
    --- a/arch/powerpc/kernel/time.c
    +++ b/arch/powerpc/kernel/time.c
    @@ -769,7 +769,7 @@ int update_persistent_clock(struct timespec now)
    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;
    @@ -787,8 +787,9 @@ unsigned long read_persistent_clock(void)
    if (!ppc_md.get_rtc_time)
    return 0;
    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 */
    diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
    index e76c2e7..a94ec48 100644
    --- a/arch/s390/kernel/time.c
    +++ b/arch/s390/kernel/time.c
    @@ -182,12 +182,9 @@ static void timing_alert_interrupt(__u16 code)
    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);
    diff --git a/arch/sh/kernel/time.c b/arch/sh/kernel/time.c
    index 9b352a1..3f4706a 100644
    --- a/arch/sh/kernel/time.c
    +++ b/arch/sh/kernel/time.c
    @@ -39,11 +39,9 @@ void (*rtc_sh_get_time)(struct timespec *) = null_rtc_get_time;
    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)
    diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
    index 5d465b2..bf67dcb 100644
    --- a/arch/x86/kernel/rtc.c
    +++ b/arch/x86/kernel/rtc.c
    @@ -178,7 +178,7 @@ static int set_rtc_mmss(unsigned long nowtime)
    }

    /* 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)
    diff --git a/arch/xtensa/kernel/time.c b/arch/xtensa/kernel/time.c
    index 8848120..19085ff 100644
    --- a/arch/xtensa/kernel/time.c
    +++ b/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);

    diff --git a/include/linux/time.h b/include/linux/time.h
    index e7c8445..53a3216 100644
    --- a/include/linux/time.h
    +++ b/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);
    diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
    index 41579e7..f1a21ce 100644
    --- a/kernel/time/timekeeping.c
    +++ b/kernel/time/timekeeping.c
    @@ -154,7 +154,7 @@ __cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock);
    */
    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_time;
    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 sys_device *dev, pm_message_t state)
    {
    unsigned long flags;

    - timekeeping_suspend_time = read_persistent_clock();
    + read_persistent_clock(&timekeeping_suspend_time);

    write_seqlock_irqsave(&xtime_lock, flags);
    timekeeping_forward_now();
    @@ -801,9 +806,10 @@ 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);
    }

    /**
    @@ -812,7 +818,7 @@ 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)

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