time: Kill xtime_lock, replacing it with jiffies_lock

Now that timekeeping is protected by its own locks, rename
the xtime_lock to jifffies_lock to better describe what it
protects.

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>

diff --git a/drivers/clocksource/i8253.c b/drivers/clocksource/i8253.c
index e7cab2da910f72724123b95d836d8a89ea2def01..14ee3efcc404d94dbd736bac6cd1d813ebfdaab2 100644 (file)
--- a/drivers/clocksource/i8253.c
+++ b/drivers/clocksource/i8253.c
@@ -35,7 +35,7 @@ static cycle_t i8253_read(struct clocksource *cs)
 
        raw_spin_lock_irqsave(&i8253_lock, flags);
        /*
-        * Although our caller may have the read side of xtime_lock,
+        * Although our caller may have the read side of jiffies_lock,
         * this is now a seqlock, and we are cheating in this routine
         * by having side effects on state that we cannot undo if
         * there is a collision on the seqlock and our caller has to

diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h
index 6b87413da9d68877bf3f65f5d85023b1f9702fc4..82ed068b1ebee619906a1713ce9e8b51c134e78c 100644 (file)
--- a/include/linux/jiffies.h
+++ b/include/linux/jiffies.h
@@ -70,11 +70,12 @@ extern int register_refined_jiffies(long clock_tick_rate);
 
 /*
  * The 64-bit value is not atomic - you MUST NOT read it
- * without sampling the sequence number in xtime_lock.
+ * without sampling the sequence number in jiffies_lock.
  * get_jiffies_64() will do this for you as appropriate.
  */
 extern u64 __jiffy_data jiffies_64;
 extern unsigned long volatile __jiffy_data jiffies;
+extern seqlock_t jiffies_lock;
 
 #if (BITS_PER_LONG < 64)
 u64 get_jiffies_64(void);

diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c
index 25f5b2699d3764f1ad546926d7c3017737d88a52..7a925ba456fb5d617d19b98daf2ca39356c4eca6 100644 (file)
--- a/kernel/time/jiffies.c
+++ b/kernel/time/jiffies.c
@@ -67,6 +67,8 @@ static struct clocksource clocksource_jiffies = {
        .shift          = JIFFIES_SHIFT,
 };
 
+__cacheline_aligned_in_smp DEFINE_SEQLOCK(jiffies_lock);
+
 #if (BITS_PER_LONG < 64)
 u64 get_jiffies_64(void)
 {
@@ -74,9 +76,9 @@ u64 get_jiffies_64(void)
        u64 ret;
 
        do {
-               seq = read_seqbegin(&xtime_lock);
+               seq = read_seqbegin(&jiffies_lock);
                ret = jiffies_64;
-       } while (read_seqretry(&xtime_lock, seq));
+       } while (read_seqretry(&jiffies_lock, seq));
        return ret;
 }
 EXPORT_SYMBOL(get_jiffies_64);

diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index da6c9ecad4e47fc0758ed70d184eec8847400b20..b1600a6973f4492d18df06483e2245443fc91201 100644 (file)
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -63,13 +63,13 @@ int tick_is_oneshot_available(void)
 static void tick_periodic(int cpu)
 {
        if (tick_do_timer_cpu == cpu) {
-               write_seqlock(&xtime_lock);
+               write_seqlock(&jiffies_lock);
 
                /* Keep track of the next tick event */
                tick_next_period = ktime_add(tick_next_period, tick_period);
 
                do_timer(1);
-               write_sequnlock(&xtime_lock);
+               write_sequnlock(&jiffies_lock);
        }
 
        update_process_times(user_mode(get_irq_regs()));
@@ -130,9 +130,9 @@ void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
                ktime_t next;
 
                do {
-                       seq = read_seqbegin(&xtime_lock);
+                       seq = read_seqbegin(&jiffies_lock);
                        next = tick_next_period;
-               } while (read_seqretry(&xtime_lock, seq));
+               } while (read_seqretry(&jiffies_lock, seq));
 
                clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 

diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index 4e265b901fedee1c00c6c09038029c443a7d53d7..cf3e59ed6dc0ce7cef9b990f74d0ace7a8a152a4 100644 (file)
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -141,4 +141,3 @@ static inline int tick_device_is_functional(struct clock_event_device *dev)
 #endif
 
 extern void do_timer(unsigned long ticks);
-extern seqlock_t xtime_lock;

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index a40260885265707603d72dee9df79f030e973221..a678046c3e5eb0cb5eebdc45719140482a197a4a 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -31,7 +31,7 @@
 static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
 
 /*
- * The time, when the last jiffy update happened. Protected by xtime_lock.
+ * The time, when the last jiffy update happened. Protected by jiffies_lock.
  */
 static ktime_t last_jiffies_update;
 
@@ -49,14 +49,14 @@ static void tick_do_update_jiffies64(ktime_t now)
        ktime_t delta;
 
        /*
-        * Do a quick check without holding xtime_lock:
+        * Do a quick check without holding jiffies_lock:
         */
        delta = ktime_sub(now, last_jiffies_update);
        if (delta.tv64 < tick_period.tv64)
                return;
 
-       /* Reevalute with xtime_lock held */
-       write_seqlock(&xtime_lock);
+       /* Reevalute with jiffies_lock held */
+       write_seqlock(&jiffies_lock);
 
        delta = ktime_sub(now, last_jiffies_update);
        if (delta.tv64 >= tick_period.tv64) {
@@ -79,7 +79,7 @@ static void tick_do_update_jiffies64(ktime_t now)
                /* Keep the tick_next_period variable up to date */
                tick_next_period = ktime_add(last_jiffies_update, tick_period);
        }
-       write_sequnlock(&xtime_lock);
+       write_sequnlock(&jiffies_lock);
 }
 
 /*
@@ -89,12 +89,12 @@ static ktime_t tick_init_jiffy_update(void)
 {
        ktime_t period;
 
-       write_seqlock(&xtime_lock);
+       write_seqlock(&jiffies_lock);
        /* Did we start the jiffies update yet ? */
        if (last_jiffies_update.tv64 == 0)
                last_jiffies_update = tick_next_period;
        period = last_jiffies_update;
-       write_sequnlock(&xtime_lock);
+       write_sequnlock(&jiffies_lock);
        return period;
 }
 
@@ -282,11 +282,11 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
 
        /* Read jiffies and the time when jiffies were updated last */
        do {
-               seq = read_seqbegin(&xtime_lock);
+               seq = read_seqbegin(&jiffies_lock);
                last_update = last_jiffies_update;
                last_jiffies = jiffies;
                time_delta = timekeeping_max_deferment();
-       } while (read_seqretry(&xtime_lock, seq));
+       } while (read_seqretry(&jiffies_lock, seq));
 
        if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) || printk_needs_cpu(cpu) ||
            arch_needs_cpu(cpu)) {
@@ -658,7 +658,7 @@ static void tick_nohz_handler(struct clock_event_device *dev)
         * concurrency: This happens only when the cpu in charge went
         * into a long sleep. If two cpus happen to assign themself to
         * this duty, then the jiffies update is still serialized by
-        * xtime_lock.
+        * jiffies_lock.
         */
        if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
                tick_do_timer_cpu = cpu;
@@ -810,7 +810,7 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
         * concurrency: This happens only when the cpu in charge went
         * into a long sleep. If two cpus happen to assign themself to
         * this duty, then the jiffies update is still serialized by
-        * xtime_lock.
+        * jiffies_lock.
         */
        if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
                tick_do_timer_cpu = cpu;

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index e424970bb562657af3d37de69320ba0f07ed9b70..4c7de02eacdce9875cefb7598d5047b95f235770 100644 (file)
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -25,12 +25,6 @@
 
 static struct timekeeper timekeeper;
 
-/*
- * This read-write spinlock protects us from races in SMP while
- * playing with xtime.
- */
-__cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock);
-
 /* flag for if timekeeping is suspended */
 int __read_mostly timekeeping_suspended;
 
@@ -1299,9 +1293,7 @@ struct timespec get_monotonic_coarse(void)
 }
 
 /*
- * The 64-bit jiffies value is not atomic - you MUST NOT read it
- * without sampling the sequence number in xtime_lock.
- * jiffies is defined in the linker script...
+ * Must hold jiffies_lock
  */
 void do_timer(unsigned long ticks)
 {
@@ -1389,7 +1381,7 @@ EXPORT_SYMBOL_GPL(ktime_get_monotonic_offset);
  */
 void xtime_update(unsigned long ticks)
 {
-       write_seqlock(&xtime_lock);
+       write_seqlock(&jiffies_lock);
        do_timer(ticks);
-       write_sequnlock(&xtime_lock);
+       write_sequnlock(&jiffies_lock);
 }