time: Add timekeeper lock

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>

1 files changed, 82 insertions, 44 deletions

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 5df2e7e556c..f5d4d226def 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);
 }
@@ -245,7 +255,7 @@ 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 +
@@ -254,7 +264,7 @@ ktime_t ktime_get(void)
                 /* If arch requires, add in gettimeoffset() */
                 nsecs += arch_gettimeoffset();
 
-        } 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.
@@ -280,14 +290,14 @@ 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();
                 /* If arch requires, add in gettimeoffset() */
                 nsecs += arch_gettimeoffset();
 
-        } 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);
@@ -315,7 +325,7 @@ 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;
@@ -328,7 +338,7 @@ 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);
@@ -362,12 +372,13 @@ 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();
 
@@ -384,7 +395,8 @@ 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();
@@ -403,12 +415,13 @@ 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();
 
@@ -422,7 +435,8 @@ 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();
@@ -494,11 +508,11 @@ 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);
 }
@@ -514,24 +528,30 @@ 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;
 }
 
 /**
@@ -576,10 +596,13 @@ 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);
@@ -597,7 +620,7 @@ 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 */
@@ -638,7 +661,7 @@ 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 */
@@ -646,7 +669,9 @@ 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);
@@ -656,7 +681,8 @@ 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();
@@ -672,14 +698,15 @@ 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);
@@ -689,7 +716,8 @@ 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();
 
@@ -701,13 +729,14 @@ 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;
 
@@ -730,7 +759,8 @@ 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();
@@ -983,10 +1013,13 @@ 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;
 
@@ -1067,6 +1100,10 @@ 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);
+
 }
 
 /**
@@ -1112,13 +1149,13 @@ 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);
@@ -1169,10 +1206,10 @@ 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;
 }
@@ -1184,11 +1221,11 @@ 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);
@@ -1220,11 +1257,11 @@ 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));
 }
 
 /**
@@ -1236,9 +1273,10 @@ 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);
 }