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    Subject[tip:timers/core] time: Provide get_xtime_and_monotonic_offset()
    Commit-ID:  48cf76f7104f655bbd48a75c7759dce82c3e1ab6
    Gitweb: http://git.kernel.org/tip/48cf76f7104f655bbd48a75c7759dce82c3e1ab6
    Author: Torben Hohn <torbenh@gmx.de>
    AuthorDate: Thu, 27 Jan 2011 15:59:05 +0100
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitDate: Mon, 31 Jan 2011 14:55:42 +0100

    time: Provide get_xtime_and_monotonic_offset()

    The hrtimer code accesses timekeeping variables under
    xtime_lock. Provide a sensible accessor function and use it.

    [ tglx: Removed the conditionals, unused variable, fixed codingstyle
    and massaged changelog ]

    Signed-off-by: Torben Hohn <torbenh@gmx.de>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: johnstul@us.ibm.com
    Cc: yong.zhang0@gmail.com
    Cc: hch@infradead.org
    LKML-Reference: <20110127145905.23248.30458.stgit@localhost>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    include/linux/time.h | 1 +
    kernel/hrtimer.c | 13 ++-----------
    kernel/time/timekeeping.c | 16 ++++++++++++++++
    3 files changed, 19 insertions(+), 11 deletions(-)

    diff --git a/include/linux/time.h b/include/linux/time.h
    index 86a9c48..4007a12 100644
    --- a/include/linux/time.h
    +++ b/include/linux/time.h
    @@ -127,6 +127,7 @@ struct timespec current_kernel_time(void);
    struct timespec __current_kernel_time(void); /* does not take xtime_lock */
    struct timespec __get_wall_to_monotonic(void); /* does not take xtime_lock */
    struct timespec get_monotonic_coarse(void);
    +void get_xtime_and_monotonic_offset(struct timespec *xtim, struct timespec *wtom);

    #define CURRENT_TIME (current_kernel_time())
    #define CURRENT_TIME_SEC ((struct timespec) { get_seconds(), 0 })
    diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
    index 0c8d7c0..57c4d33 100644
    --- a/kernel/hrtimer.c
    +++ b/kernel/hrtimer.c
    @@ -85,13 +85,8 @@ static void hrtimer_get_softirq_time(struct hrtimer_cpu_base *base)
    {
    ktime_t xtim, tomono;
    struct timespec xts, tom;
    - unsigned long seq;

    - do {
    - seq = read_seqbegin(&xtime_lock);
    - xts = __current_kernel_time();
    - tom = __get_wall_to_monotonic();
    - } while (read_seqretry(&xtime_lock, seq));
    + get_xtime_and_monotonic_offset(&xts, &tom);

    xtim = timespec_to_ktime(xts);
    tomono = timespec_to_ktime(tom);
    @@ -612,15 +607,11 @@ static void retrigger_next_event(void *arg)
    {
    struct hrtimer_cpu_base *base;
    struct timespec realtime_offset, wtm;
    - unsigned long seq;

    if (!hrtimer_hres_active())
    return;

    - do {
    - seq = read_seqbegin(&xtime_lock);
    - wtm = __get_wall_to_monotonic();
    - } while (read_seqretry(&xtime_lock, seq));
    + get_xtime_and_monotonic_offset(&realtime_offset, &wtm);
    set_normalized_timespec(&realtime_offset, -wtm.tv_sec, -wtm.tv_nsec);

    base = &__get_cpu_var(hrtimer_bases);
    diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
    index c1a178c..c50aaf6 100644
    --- a/kernel/time/timekeeping.c
    +++ b/kernel/time/timekeeping.c
    @@ -958,3 +958,19 @@ void do_timer(unsigned long ticks)
    update_wall_time();
    calc_global_load(ticks);
    }
    +
    +/**
    + * get_xtime_and_monotonic_offset() - get xtime and wall_to_monotonic
    + * @xtim: pointer to timespec to be set with xtime
    + * @wtom: pointer to timespec to be set with wall_to_monotonic
    + */
    +void get_xtime_and_monotonic_offset(struct timespec *xtim, struct timespec *wtom)
    +{
    + unsigned long seq;
    +
    + do {
    + seq = read_seqbegin(&xtime_lock);
    + *xtim = xtime;
    + *wtom = wall_to_monotonic;
    + } while (read_seqretry(&xtime_lock, seq));
    +}

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