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Subject[PATCH 06/16] time: Add timekeeper lock
Date
Now that all the timekeeping variables are stored in
the timekeeper structure, add a new lock to protect the
structure.

For now, this lock nests under the xtime_lock for writes.

For readers, we don't need to take xtime_lock anymore.

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 | 126 +++++++++++++++++++++++++++++----------------
1 files changed, 82 insertions(+), 44 deletions(-)

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 78872ba..8f54200 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -69,6 +69,9 @@ struct timekeeper {
struct timespec total_sleep_time;
/* The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock. */
struct timespec raw_time;
+
+ /* Seqlock for all timekeeper values */
+ seqlock_t lock;
};

static struct timekeeper timekeeper;
@@ -172,10 +175,17 @@ static inline s64 timekeeping_get_ns_raw(void)
/* must hold xtime_lock */
void timekeeping_leap_insert(int leapsecond)
{
+ unsigned long flags;
+
+ write_seqlock_irqsave(&timekeeper.lock, flags);
+
timekeeper.xtime.tv_sec += leapsecond;
timekeeper.wall_to_monotonic.tv_sec -= leapsecond;
update_vsyscall(&timekeeper.xtime, &timekeeper.wall_to_monotonic,
timekeeper.clock, timekeeper.mult);
+
+ write_sequnlock_irqrestore(&timekeeper.lock, flags);
+
}

/**
@@ -222,7 +232,7 @@ void getnstimeofday(struct timespec *ts)
WARN_ON(timekeeping_suspended);

do {
- seq = read_seqbegin(&xtime_lock);
+ seq = read_seqbegin(&timekeeper.lock);

*ts = timekeeper.xtime;
nsecs = timekeeping_get_ns();
@@ -230,7 +240,7 @@ void getnstimeofday(struct timespec *ts)
/* If arch requires, add in gettimeoffset() */
nsecs += arch_gettimeoffset();

- } while (read_seqretry(&xtime_lock, seq));
+ } while (read_seqretry(&timekeeper.lock, seq));

timespec_add_ns(ts, nsecs);
}
@@ -245,14 +255,14 @@ ktime_t ktime_get(void)
WARN_ON(timekeeping_suspended);

do {
- seq = read_seqbegin(&xtime_lock);
+ seq = read_seqbegin(&timekeeper.lock);
secs = timekeeper.xtime.tv_sec +
timekeeper.wall_to_monotonic.tv_sec;
nsecs = timekeeper.xtime.tv_nsec +
timekeeper.wall_to_monotonic.tv_nsec;
nsecs += timekeeping_get_ns();

- } while (read_seqretry(&xtime_lock, seq));
+ } while (read_seqretry(&timekeeper.lock, seq));
/*
* Use ktime_set/ktime_add_ns to create a proper ktime on
* 32-bit architectures without CONFIG_KTIME_SCALAR.
@@ -278,12 +288,12 @@ void ktime_get_ts(struct timespec *ts)
WARN_ON(timekeeping_suspended);

do {
- seq = read_seqbegin(&xtime_lock);
+ seq = read_seqbegin(&timekeeper.lock);
*ts = timekeeper.xtime;
tomono = timekeeper.wall_to_monotonic;
nsecs = timekeeping_get_ns();

- } while (read_seqretry(&xtime_lock, seq));
+ } while (read_seqretry(&timekeeper.lock, seq));

set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
ts->tv_nsec + tomono.tv_nsec + nsecs);
@@ -311,7 +321,7 @@ void getnstime_raw_and_real(struct timespec *ts_raw, struct timespec *ts_real)
do {
u32 arch_offset;

- seq = read_seqbegin(&xtime_lock);
+ seq = read_seqbegin(&timekeeper.lock);

*ts_raw = timekeeper.raw_time;
*ts_real = timekeeper.xtime;
@@ -324,7 +334,7 @@ void getnstime_raw_and_real(struct timespec *ts_raw, struct timespec *ts_real)
nsecs_raw += arch_offset;
nsecs_real += arch_offset;

- } while (read_seqretry(&xtime_lock, seq));
+ } while (read_seqretry(&timekeeper.lock, seq));

timespec_add_ns(ts_raw, nsecs_raw);
timespec_add_ns(ts_real, nsecs_real);
@@ -358,12 +368,13 @@ EXPORT_SYMBOL(do_gettimeofday);
int do_settimeofday(const struct timespec *tv)
{
struct timespec ts_delta;
- unsigned long flags;
+ unsigned long flags1,flags2;

if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
return -EINVAL;

- write_seqlock_irqsave(&xtime_lock, flags);
+ write_seqlock_irqsave(&xtime_lock, flags1);
+ write_seqlock_irqsave(&timekeeper.lock, flags2);

timekeeping_forward_now();

@@ -380,7 +391,8 @@ int do_settimeofday(const struct timespec *tv)
update_vsyscall(&timekeeper.xtime, &timekeeper.wall_to_monotonic,
timekeeper.clock, timekeeper.mult);

- write_sequnlock_irqrestore(&xtime_lock, flags);
+ write_sequnlock_irqrestore(&timekeeper.lock, flags2);
+ write_sequnlock_irqrestore(&xtime_lock, flags1);

/* signal hrtimers about time change */
clock_was_set();
@@ -399,12 +411,13 @@ EXPORT_SYMBOL(do_settimeofday);
*/
int timekeeping_inject_offset(struct timespec *ts)
{
- unsigned long flags;
+ unsigned long flags1,flags2;

if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC)
return -EINVAL;

- write_seqlock_irqsave(&xtime_lock, flags);
+ write_seqlock_irqsave(&xtime_lock, flags1);
+ write_seqlock_irqsave(&timekeeper.lock, flags2);

timekeeping_forward_now();

@@ -418,7 +431,8 @@ int timekeeping_inject_offset(struct timespec *ts)
update_vsyscall(&timekeeper.xtime, &timekeeper.wall_to_monotonic,
timekeeper.clock, timekeeper.mult);

- write_sequnlock_irqrestore(&xtime_lock, flags);
+ write_sequnlock_irqrestore(&timekeeper.lock, flags2);
+ write_sequnlock_irqrestore(&xtime_lock, flags1);

/* signal hrtimers about time change */
clock_was_set();
@@ -490,11 +504,11 @@ void getrawmonotonic(struct timespec *ts)
s64 nsecs;

do {
- seq = read_seqbegin(&xtime_lock);
+ seq = read_seqbegin(&timekeeper.lock);
nsecs = timekeeping_get_ns_raw();
*ts = timekeeper.raw_time;

- } while (read_seqretry(&xtime_lock, seq));
+ } while (read_seqretry(&timekeeper.lock, seq));

timespec_add_ns(ts, nsecs);
}
@@ -510,24 +524,30 @@ int timekeeping_valid_for_hres(void)
int ret;

do {
- seq = read_seqbegin(&xtime_lock);
+ seq = read_seqbegin(&timekeeper.lock);

ret = timekeeper.clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;

- } while (read_seqretry(&xtime_lock, seq));
+ } while (read_seqretry(&timekeeper.lock, seq));

return ret;
}

/**
* timekeeping_max_deferment - Returns max time the clocksource can be deferred
- *
- * Caller must observe xtime_lock via read_seqbegin/read_seqretry to
- * ensure that the clocksource does not change!
*/
u64 timekeeping_max_deferment(void)
{
- return timekeeper.clock->max_idle_ns;
+ unsigned long seq;
+ u64 ret;
+ do {
+ seq = read_seqbegin(&timekeeper.lock);
+
+ ret = timekeeper.clock->max_idle_ns;
+
+ } while (read_seqretry(&timekeeper.lock, seq));
+
+ return ret;
}

/**
@@ -572,10 +592,13 @@ void __init timekeeping_init(void)
read_persistent_clock(&now);
read_boot_clock(&boot);

- write_seqlock_irqsave(&xtime_lock, flags);
+ seqlock_init(&timekeeper.lock);

+ write_seqlock_irqsave(&xtime_lock, flags);
ntp_init();
+ write_sequnlock_irqrestore(&xtime_lock, flags);

+ write_seqlock_irqsave(&timekeeper.lock, flags);
clock = clocksource_default_clock();
if (clock->enable)
clock->enable(clock);
@@ -593,7 +616,7 @@ void __init timekeeping_init(void)
-boot.tv_sec, -boot.tv_nsec);
timekeeper.total_sleep_time.tv_sec = 0;
timekeeper.total_sleep_time.tv_nsec = 0;
- write_sequnlock_irqrestore(&xtime_lock, flags);
+ write_sequnlock_irqrestore(&timekeeper.lock, flags);
}

/* time in seconds when suspend began */
@@ -634,7 +657,7 @@ static void __timekeeping_inject_sleeptime(struct timespec *delta)
*/
void timekeeping_inject_sleeptime(struct timespec *delta)
{
- unsigned long flags;
+ unsigned long flags1,flags2;
struct timespec ts;

/* Make sure we don't set the clock twice */
@@ -642,7 +665,9 @@ void timekeeping_inject_sleeptime(struct timespec *delta)
if (!(ts.tv_sec == 0 && ts.tv_nsec == 0))
return;

- write_seqlock_irqsave(&xtime_lock, flags);
+ write_seqlock_irqsave(&xtime_lock, flags1);
+ write_seqlock_irqsave(&timekeeper.lock, flags2);
+
timekeeping_forward_now();

__timekeeping_inject_sleeptime(delta);
@@ -652,7 +677,8 @@ void timekeeping_inject_sleeptime(struct timespec *delta)
update_vsyscall(&timekeeper.xtime, &timekeeper.wall_to_monotonic,
timekeeper.clock, timekeeper.mult);

- write_sequnlock_irqrestore(&xtime_lock, flags);
+ write_sequnlock_irqrestore(&timekeeper.lock, flags2);
+ write_sequnlock_irqrestore(&xtime_lock, flags1);

/* signal hrtimers about time change */
clock_was_set();
@@ -668,14 +694,15 @@ void timekeeping_inject_sleeptime(struct timespec *delta)
*/
static void timekeeping_resume(void)
{
- unsigned long flags;
+ unsigned long flags1,flags2;
struct timespec ts;

read_persistent_clock(&ts);

clocksource_resume();

- write_seqlock_irqsave(&xtime_lock, flags);
+ write_seqlock_irqsave(&xtime_lock, flags1);
+ write_seqlock_irqsave(&timekeeper.lock, flags2);

if (timespec_compare(&ts, &timekeeping_suspend_time) > 0) {
ts = timespec_sub(ts, timekeeping_suspend_time);
@@ -685,7 +712,8 @@ static void timekeeping_resume(void)
timekeeper.clock->cycle_last = timekeeper.clock->read(timekeeper.clock);
timekeeper.ntp_error = 0;
timekeeping_suspended = 0;
- write_sequnlock_irqrestore(&xtime_lock, flags);
+ write_sequnlock_irqrestore(&timekeeper.lock, flags2);
+ write_sequnlock_irqrestore(&xtime_lock, flags1);

touch_softlockup_watchdog();

@@ -697,13 +725,14 @@ static void timekeeping_resume(void)

static int timekeeping_suspend(void)
{
- unsigned long flags;
+ unsigned long flags1,flags2;
struct timespec delta, delta_delta;
static struct timespec old_delta;

read_persistent_clock(&timekeeping_suspend_time);

- write_seqlock_irqsave(&xtime_lock, flags);
+ write_seqlock_irqsave(&xtime_lock, flags1);
+ write_seqlock_irqsave(&timekeeper.lock, flags2);
timekeeping_forward_now();
timekeeping_suspended = 1;

@@ -726,7 +755,8 @@ static int timekeeping_suspend(void)
timekeeping_suspend_time =
timespec_add(timekeeping_suspend_time, delta_delta);
}
- write_sequnlock_irqrestore(&xtime_lock, flags);
+ write_sequnlock_irqrestore(&timekeeper.lock, flags2);
+ write_sequnlock_irqrestore(&xtime_lock, flags1);

clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
clocksource_suspend();
@@ -893,10 +923,13 @@ static void update_wall_time(void)
struct clocksource *clock;
cycle_t offset;
int shift = 0, maxshift;
+ unsigned long flags;
+
+ write_seqlock_irqsave(&timekeeper.lock, flags);

/* Make sure we're fully resumed: */
if (unlikely(timekeeping_suspended))
- return;
+ goto out;

clock = timekeeper.clock;

@@ -977,6 +1010,10 @@ static void update_wall_time(void)
/* check to see if there is a new clocksource to use */
update_vsyscall(&timekeeper.xtime, &timekeeper.wall_to_monotonic,
timekeeper.clock, timekeeper.mult);
+
+out:
+ write_sequnlock_irqrestore(&timekeeper.lock, flags);
+
}

/**
@@ -1022,13 +1059,13 @@ void get_monotonic_boottime(struct timespec *ts)
WARN_ON(timekeeping_suspended);

do {
- seq = read_seqbegin(&xtime_lock);
+ seq = read_seqbegin(&timekeeper.lock);
*ts = timekeeper.xtime;
tomono = timekeeper.wall_to_monotonic;
sleep = timekeeper.total_sleep_time;
nsecs = timekeeping_get_ns();

- } while (read_seqretry(&xtime_lock, seq));
+ } while (read_seqretry(&timekeeper.lock, seq));

set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec + sleep.tv_sec,
ts->tv_nsec + tomono.tv_nsec + sleep.tv_nsec + nsecs);
@@ -1079,10 +1116,10 @@ struct timespec current_kernel_time(void)
unsigned long seq;

do {
- seq = read_seqbegin(&xtime_lock);
+ seq = read_seqbegin(&timekeeper.lock);

now = timekeeper.xtime;
- } while (read_seqretry(&xtime_lock, seq));
+ } while (read_seqretry(&timekeeper.lock, seq));

return now;
}
@@ -1094,11 +1131,11 @@ struct timespec get_monotonic_coarse(void)
unsigned long seq;

do {
- seq = read_seqbegin(&xtime_lock);
+ seq = read_seqbegin(&timekeeper.lock);

now = timekeeper.xtime;
mono = timekeeper.wall_to_monotonic;
- } while (read_seqretry(&xtime_lock, seq));
+ } while (read_seqretry(&timekeeper.lock, seq));

set_normalized_timespec(&now, now.tv_sec + mono.tv_sec,
now.tv_nsec + mono.tv_nsec);
@@ -1130,11 +1167,11 @@ void get_xtime_and_monotonic_and_sleep_offset(struct timespec *xtim,
unsigned long seq;

do {
- seq = read_seqbegin(&xtime_lock);
+ seq = read_seqbegin(&timekeeper.lock);
*xtim = timekeeper.xtime;
*wtom = timekeeper.wall_to_monotonic;
*sleep = timekeeper.total_sleep_time;
- } while (read_seqretry(&xtime_lock, seq));
+ } while (read_seqretry(&timekeeper.lock, seq));
}

/**
@@ -1146,9 +1183,10 @@ ktime_t ktime_get_monotonic_offset(void)
struct timespec wtom;

do {
- seq = read_seqbegin(&xtime_lock);
+ seq = read_seqbegin(&timekeeper.lock);
wtom = timekeeper.wall_to_monotonic;
- } while (read_seqretry(&xtime_lock, seq));
+ } while (read_seqretry(&timekeeper.lock, seq));
+
return timespec_to_ktime(wtom);
}

--
1.7.3.2.146.gca209


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