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    Subject[PATCH 5/9] time: Shadow cycle_last in timekeeper structure
    Date
    The clocksource cycle_last value is problematic for working on
    shadow copies of the timekeeper, because the clocksource is global.

    Since its mostly used only for timekeeping, move cycle_last into
    the timekeeper. Unfortunately there are some uses for cycle_last
    outside of timekeeping (such as tsc_read, which makes sure we haven't
    skipped to a core that the TSC is behind the last read), so we
    keep the clocksource cycle_last updated as well.

    CC: Ingo Molnar <mingo@elte.hu>
    CC: Thomas Gleixner <tglx@linutronix.de>
    CC: Eric Dumazet <eric.dumazet@gmail.com>
    CC: Richard Cochran <richardcochran@gmail.com>
    Signed-off-by: John Stultz <john.stultz@linaro.org>
    ---
    kernel/time/timekeeping.c | 23 ++++++++++++++---------
    1 files changed, 14 insertions(+), 9 deletions(-)

    diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
    index 09460c1..ed8cb51 100644
    --- a/kernel/time/timekeeping.c
    +++ b/kernel/time/timekeeping.c
    @@ -29,7 +29,8 @@ struct timekeeper {
    u32 mult;
    /* The shift value of the current clocksource. */
    int shift;
    -
    + /* cycle value at last accumulation point */
    + cycle_t cycle_last;
    /* Number of clock cycles in one NTP interval. */
    cycle_t cycle_interval;
    /* Number of clock shifted nano seconds in one NTP interval. */
    @@ -142,7 +143,8 @@ static void tk_setup_internals(struct timekeeper *tk, struct clocksource *clock)

    old_clock = tk->clock;
    tk->clock = clock;
    - clock->cycle_last = clock->read(clock);
    + tk->cycle_last = clock->read(clock);
    + clock->cycle_last = tk->cycle_last;

    /* Do the ns -> cycle conversion first, using original mult */
    tmp = NTP_INTERVAL_LENGTH;
    @@ -195,7 +197,7 @@ static inline s64 timekeeping_get_ns(struct timekeeper *tk)
    cycle_now = clock->read(clock);

    /* calculate the delta since the last update_wall_time: */
    - cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
    + cycle_delta = (cycle_now - tk->cycle_last) & clock->mask;

    nsec = cycle_delta * tk->mult + tk->xtime_nsec;
    return nsec >> tk->shift;
    @@ -211,7 +213,7 @@ static inline s64 timekeeping_get_ns_raw(struct timekeeper *tk)
    cycle_now = clock->read(clock);

    /* calculate the delta since the last update_wall_time: */
    - cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
    + cycle_delta = (cycle_now - tk->cycle_last) & clock->mask;

    /* return delta convert to nanoseconds. */
    return clocksource_cyc2ns(cycle_delta, clock->mult, clock->shift);
    @@ -259,8 +261,9 @@ static void timekeeping_forward_now(struct timekeeper *tk)

    clock = tk->clock;
    cycle_now = clock->read(clock);
    - cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
    - clock->cycle_last = cycle_now;
    + cycle_delta = (cycle_now - tk->cycle_last) & clock->mask;
    + tk->cycle_last = cycle_now;
    + tk->clock->cycle_last = cycle_now;

    tk->xtime_nsec += cycle_delta * tk->mult;

    @@ -760,7 +763,8 @@ static void timekeeping_resume(void)
    __timekeeping_inject_sleeptime(&ts);
    }
    /* re-base the last cycle value */
    - timekeeper.clock->cycle_last = timekeeper.clock->read(timekeeper.clock);
    + timekeeper.cycle_last = timekeeper.clock->read(timekeeper.clock);
    + timekeeper.clock->cycle_last = timekeeper.cycle_last;
    timekeeper.ntp_error = 0;
    timekeeping_suspended = 0;

    @@ -1026,7 +1030,7 @@ static cycle_t logarithmic_accumulation(struct timekeeper *tk, cycle_t offset,

    /* Accumulate one shifted interval */
    offset -= tk->cycle_interval << shift;
    - tk->clock->cycle_last += tk->cycle_interval << shift;
    + tk->cycle_last += tk->cycle_interval << shift;

    tk->xtime_nsec += tk->xtime_interval << shift;
    while (tk->xtime_nsec >= nsecps) {
    @@ -1079,7 +1083,7 @@ static void update_wall_time(void)
    #ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
    offset = shadow_tk.cycle_interval;
    #else
    - offset = (clock->read(clock) - clock->cycle_last) & clock->mask;
    + offset = (clock->read(clock) - shadow_tk.cycle_last) & clock->mask;
    #endif

    /*
    @@ -1153,6 +1157,7 @@ static void update_wall_time(void)


    timekeeper = shadow_tk;
    + timekeeper.clock->cycle_last = timekeeper.cycle_last;
    timekeeping_update(&timekeeper, false);

    out:
    --
    1.7.3.2.146.gca209


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