timekeeping-split-xtime-lock.patch

Subject: timekeeping: Split xtime_lock
From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 01 Mar 2012 15:14:06 +0100

xtime_lock is going to be split apart in mainline, so we can shorten
the seqcount protected regions and avoid updating seqcount in some
code pathes. This is a straight forward split, so we can avoid the
whole mess with raw seqlocks for RT.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/time/jiffies.c       |    4 -
 kernel/time/tick-common.c   |   10 ++-
 kernel/time/tick-internal.h |    3 -
 kernel/time/tick-sched.c    |   16 +++---
 kernel/time/timekeeping.c   |  116 +++++++++++++++++++++++++-------------------
 5 files changed, 88 insertions(+), 61 deletions(-)

Index: linux-stable/kernel/time/jiffies.c
===================================================================
--- linux-stable.orig/kernel/time/jiffies.c
+++ linux-stable/kernel/time/jiffies.c
@@ -74,9 +74,9 @@ u64 get_jiffies_64(void)
 	u64 ret;
 
 	do {
-		seq = read_seqbegin(&xtime_lock);
+		seq = read_seqcount_begin(&xtime_seq);
 		ret = jiffies_64;
-	} while (read_seqretry(&xtime_lock, seq));
+	} while (read_seqcount_retry(&xtime_seq, seq));
 	return ret;
 }
 EXPORT_SYMBOL(get_jiffies_64);
Index: linux-stable/kernel/time/tick-common.c
===================================================================
--- linux-stable.orig/kernel/time/tick-common.c
+++ linux-stable/kernel/time/tick-common.c
@@ -63,13 +63,15 @@ int tick_is_oneshot_available(void)
 static void tick_periodic(int cpu)
 {
 	if (tick_do_timer_cpu == cpu) {
-		write_seqlock(&xtime_lock);
+		raw_spin_lock(&xtime_lock);
+		write_seqcount_begin(&xtime_seq);
 
 		/* 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_seqcount_end(&xtime_seq);
+		raw_spin_unlock(&xtime_lock);
 	}
 
 	update_process_times(user_mode(get_irq_regs()));
@@ -130,9 +132,9 @@ void tick_setup_periodic(struct clock_ev
 		ktime_t next;
 
 		do {
-			seq = read_seqbegin(&xtime_lock);
+			seq = read_seqcount_begin(&xtime_seq);
 			next = tick_next_period;
-		} while (read_seqretry(&xtime_lock, seq));
+		} while (read_seqcount_retry(&xtime_seq, seq));
 
 		clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 
Index: linux-stable/kernel/time/tick-internal.h
===================================================================
--- linux-stable.orig/kernel/time/tick-internal.h
+++ linux-stable/kernel/time/tick-internal.h
@@ -141,4 +141,5 @@ static inline int tick_device_is_functio
 #endif
 
 extern void do_timer(unsigned long ticks);
-extern seqlock_t xtime_lock;
+extern raw_spinlock_t xtime_lock;
+extern seqcount_t xtime_seq;
Index: linux-stable/kernel/time/tick-sched.c
===================================================================
--- linux-stable.orig/kernel/time/tick-sched.c
+++ linux-stable/kernel/time/tick-sched.c
@@ -56,7 +56,8 @@ static void tick_do_update_jiffies64(kti
 		return;
 
 	/* Reevalute with xtime_lock held */
-	write_seqlock(&xtime_lock);
+	raw_spin_lock(&xtime_lock);
+	write_seqcount_begin(&xtime_seq);
 
 	delta = ktime_sub(now, last_jiffies_update);
 	if (delta.tv64 >= tick_period.tv64) {
@@ -79,7 +80,8 @@ static void tick_do_update_jiffies64(kti
 		/* Keep the tick_next_period variable up to date */
 		tick_next_period = ktime_add(last_jiffies_update, tick_period);
 	}
-	write_sequnlock(&xtime_lock);
+	write_seqcount_end(&xtime_seq);
+	raw_spin_unlock(&xtime_lock);
 }
 
 /*
@@ -89,12 +91,14 @@ static ktime_t tick_init_jiffy_update(vo
 {
 	ktime_t period;
 
-	write_seqlock(&xtime_lock);
+	raw_spin_lock(&xtime_lock);
+	write_seqcount_begin(&xtime_seq);
 	/* 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_seqcount_end(&xtime_seq);
+	raw_spin_unlock(&xtime_lock);
 	return period;
 }
 
@@ -282,11 +286,11 @@ static ktime_t tick_nohz_stop_sched_tick
 
 	/* Read jiffies and the time when jiffies were updated last */
 	do {
-		seq = read_seqbegin(&xtime_lock);
+		seq = read_seqcount_begin(&xtime_seq);
 		last_update = last_jiffies_update;
 		last_jiffies = jiffies;
 		time_delta = timekeeping_max_deferment();
-	} while (read_seqretry(&xtime_lock, seq));
+	} while (read_seqcount_retry(&xtime_seq, seq));
 
 	if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) || printk_needs_cpu(cpu) ||
 	    arch_needs_cpu(cpu)) {
Index: linux-stable/kernel/time/timekeeping.c
===================================================================
--- linux-stable.orig/kernel/time/timekeeping.c
+++ linux-stable/kernel/time/timekeeping.c
@@ -74,7 +74,8 @@ struct timekeeper {
 	/* The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock. */
 	struct timespec		raw_time;
 	/* Seqlock for all timekeeper values */
-	seqlock_t		lock;
+	seqcount_t		seq;
+	raw_spinlock_t		lock;
 };
 
 static struct timekeeper timekeeper;
@@ -83,7 +84,8 @@ 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);
+__cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(xtime_lock);
+seqcount_t xtime_seq;
 
 /* flag for if timekeeping is suspended */
 int __read_mostly timekeeping_suspended;
@@ -300,12 +302,12 @@ void getnstimeofday(struct timespec *ts)
 	WARN_ON(timekeeping_suspended);
 
 	do {
-		seq = read_seqbegin(&tk->lock);
+		seq = read_seqcount_begin(&tk->seq);
 
 		ts->tv_sec = tk->xtime_sec;
 		nsecs = timekeeping_get_ns(tk);
 
-	} while (read_seqretry(&tk->lock, seq));
+	} while (read_seqcount_retry(&tk->seq, seq));
 
 	ts->tv_nsec = 0;
 	timespec_add_ns(ts, nsecs);
@@ -321,11 +323,11 @@ ktime_t ktime_get(void)
 	WARN_ON(timekeeping_suspended);
 
 	do {
-		seq = read_seqbegin(&tk->lock);
+		seq = read_seqcount_begin(&tk->seq);
 		secs = tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
 		nsecs = timekeeping_get_ns(tk) + tk->wall_to_monotonic.tv_nsec;
 
-	} while (read_seqretry(&tk->lock, seq));
+	} while (read_seqcount_retry(&tk->seq, seq));
 	/*
 	 * Use ktime_set/ktime_add_ns to create a proper ktime on
 	 * 32-bit architectures without CONFIG_KTIME_SCALAR.
@@ -352,12 +354,12 @@ void ktime_get_ts(struct timespec *ts)
 	WARN_ON(timekeeping_suspended);
 
 	do {
-		seq = read_seqbegin(&tk->lock);
+		seq = read_seqcount_begin(&tk->seq);
 		ts->tv_sec = tk->xtime_sec;
 		nsec = timekeeping_get_ns(tk);
 		tomono = tk->wall_to_monotonic;
 
-	} while (read_seqretry(&tk->lock, seq));
+	} while (read_seqcount_retry(&tk->seq, seq));
 
 	ts->tv_sec += tomono.tv_sec;
 	ts->tv_nsec = 0;
@@ -385,7 +387,7 @@ void getnstime_raw_and_real(struct times
 	WARN_ON_ONCE(timekeeping_suspended);
 
 	do {
-		seq = read_seqbegin(&tk->lock);
+		seq = read_seqcount_begin(&tk->seq);
 
 		*ts_raw = tk->raw_time;
 		ts_real->tv_sec = tk->xtime_sec;
@@ -394,7 +396,7 @@ void getnstime_raw_and_real(struct times
 		nsecs_raw = timekeeping_get_ns_raw(tk);
 		nsecs_real = timekeeping_get_ns(tk);
 
-	} while (read_seqretry(&tk->lock, seq));
+	} while (read_seqcount_retry(&tk->seq, seq));
 
 	timespec_add_ns(ts_raw, nsecs_raw);
 	timespec_add_ns(ts_real, nsecs_real);
@@ -434,7 +436,8 @@ int do_settimeofday(const struct timespe
 	if (!timespec_valid_strict(tv))
 		return -EINVAL;
 
-	write_seqlock_irqsave(&tk->lock, flags);
+	raw_spin_lock_irqsave(&tk->lock, flags);
+	write_seqcount_begin(&tk->seq);
 
 	timekeeping_forward_now(tk);
 
@@ -448,7 +451,8 @@ int do_settimeofday(const struct timespe
 
 	timekeeping_update(tk, true);
 
-	write_sequnlock_irqrestore(&tk->lock, flags);
+	write_seqcount_end(&tk->seq);
+	raw_spin_unlock_irqrestore(&tk->lock, flags);
 
 	/* signal hrtimers about time change */
 	clock_was_set();
@@ -473,7 +477,8 @@ int timekeeping_inject_offset(struct tim
 	if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC)
 		return -EINVAL;
 
-	write_seqlock_irqsave(&tk->lock, flags);
+	raw_spin_lock_irqsave(&tk->lock, flags);
+	write_seqcount_begin(&tk->seq);
 
 	timekeeping_forward_now(tk);
 
@@ -490,7 +495,8 @@ int timekeeping_inject_offset(struct tim
 error: /* even if we error out, we forwarded the time, so call update */
 	timekeeping_update(tk, true);
 
-	write_sequnlock_irqrestore(&tk->lock, flags);
+	write_seqcount_end(&tk->seq);
+	raw_spin_unlock_irqrestore(&tk->lock, flags);
 
 	/* signal hrtimers about time change */
 	clock_was_set();
@@ -512,7 +518,8 @@ static int change_clocksource(void *data
 
 	new = (struct clocksource *) data;
 
-	write_seqlock_irqsave(&tk->lock, flags);
+	raw_spin_lock_irqsave(&tk->lock, flags);
+	write_seqcount_begin(&tk->seq);
 
 	timekeeping_forward_now(tk);
 	if (!new->enable || new->enable(new) == 0) {
@@ -523,7 +530,8 @@ static int change_clocksource(void *data
 	}
 	timekeeping_update(tk, true);
 
-	write_sequnlock_irqrestore(&tk->lock, flags);
+	write_seqcount_end(&tk->seq);
+	raw_spin_unlock_irqrestore(&tk->lock, flags);
 
 	return 0;
 }
@@ -573,11 +581,11 @@ void getrawmonotonic(struct timespec *ts
 	s64 nsecs;
 
 	do {
-		seq = read_seqbegin(&tk->lock);
+		seq = read_seqcount_begin(&tk->seq);
 		nsecs = timekeeping_get_ns_raw(tk);
 		*ts = tk->raw_time;
 
-	} while (read_seqretry(&tk->lock, seq));
+	} while (read_seqcount_retry(&tk->seq, seq));
 
 	timespec_add_ns(ts, nsecs);
 }
@@ -593,11 +601,11 @@ int timekeeping_valid_for_hres(void)
 	int ret;
 
 	do {
-		seq = read_seqbegin(&tk->lock);
+		seq = read_seqcount_begin(&tk->seq);
 
 		ret = tk->clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
 
-	} while (read_seqretry(&tk->lock, seq));
+	} while (read_seqcount_retry(&tk->seq, seq));
 
 	return ret;
 }
@@ -612,11 +620,11 @@ u64 timekeeping_max_deferment(void)
 	u64 ret;
 
 	do {
-		seq = read_seqbegin(&tk->lock);
+		seq = read_seqcount_begin(&tk->seq);
 
 		ret = tk->clock->max_idle_ns;
 
-	} while (read_seqretry(&tk->lock, seq));
+	} while (read_seqcount_retry(&tk->seq, seq));
 
 	return ret;
 }
@@ -677,11 +685,13 @@ void __init timekeeping_init(void)
 		boot.tv_nsec = 0;
 	}
 
-	seqlock_init(&tk->lock);
+	raw_spin_lock_init(&tk->lock);
+	seqcount_init(&tk->seq);
 
 	ntp_init();
 
-	write_seqlock_irqsave(&tk->lock, flags);
+	raw_spin_lock_irqsave(&tk->lock, flags);
+	write_seqcount_begin(&tk->seq);
 	clock = clocksource_default_clock();
 	if (clock->enable)
 		clock->enable(clock);
@@ -700,7 +710,8 @@ void __init timekeeping_init(void)
 	tmp.tv_nsec = 0;
 	tk_set_sleep_time(tk, tmp);
 
-	write_sequnlock_irqrestore(&tk->lock, flags);
+	write_seqcount_end(&tk->seq);
+	raw_spin_unlock_irqrestore(&tk->lock, flags);
 }
 
 /* time in seconds when suspend began */
@@ -747,7 +758,8 @@ void timekeeping_inject_sleeptime(struct
 	if (!(ts.tv_sec == 0 && ts.tv_nsec == 0))
 		return;
 
-	write_seqlock_irqsave(&tk->lock, flags);
+	raw_spin_lock_irqsave(&tk->lock, flags);
+	write_seqcount_begin(&tk->seq);
 
 	timekeeping_forward_now(tk);
 
@@ -755,7 +767,8 @@ void timekeeping_inject_sleeptime(struct
 
 	timekeeping_update(tk, true);
 
-	write_sequnlock_irqrestore(&tk->lock, flags);
+	write_seqcount_end(&tk->seq);
+	raw_spin_unlock_irqrestore(&tk->lock, flags);
 
 	/* signal hrtimers about time change */
 	clock_was_set();
@@ -778,7 +791,8 @@ static void timekeeping_resume(void)
 
 	clocksource_resume();
 
-	write_seqlock_irqsave(&tk->lock, flags);
+	raw_spin_lock_irqsave(&tk->lock, flags);
+	write_seqcount_begin(&tk->seq);
 
 	if (timespec_compare(&ts, &timekeeping_suspend_time) > 0) {
 		ts = timespec_sub(ts, timekeeping_suspend_time);
@@ -789,7 +803,8 @@ static void timekeeping_resume(void)
 	tk->ntp_error = 0;
 	timekeeping_suspended = 0;
 	timekeeping_update(tk, false);
-	write_sequnlock_irqrestore(&tk->lock, flags);
+	write_seqcount_end(&tk->seq);
+	raw_spin_unlock_irqrestore(&tk->lock, flags);
 
 	touch_softlockup_watchdog();
 
@@ -808,7 +823,8 @@ static int timekeeping_suspend(void)
 
 	read_persistent_clock(&timekeeping_suspend_time);
 
-	write_seqlock_irqsave(&tk->lock, flags);
+	raw_spin_lock_irqsave(&tk->lock, flags);
+	write_seqcount_begin(&tk->seq);
 	timekeeping_forward_now(tk);
 	timekeeping_suspended = 1;
 
@@ -831,7 +847,8 @@ static int timekeeping_suspend(void)
 		timekeeping_suspend_time =
 			timespec_add(timekeeping_suspend_time, delta_delta);
 	}
-	write_sequnlock_irqrestore(&tk->lock, flags);
+	write_seqcount_end(&tk->seq);
+	raw_spin_unlock_irqrestore(&tk->lock, flags);
 
 	clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
 	clocksource_suspend();
@@ -1141,7 +1158,8 @@ static void update_wall_time(void)
 	unsigned long flags;
 	s64 remainder;
 
-	write_seqlock_irqsave(&tk->lock, flags);
+	raw_spin_lock_irqsave(&tk->lock, flags);
+	write_seqcount_begin(&tk->seq);
 
 	/* Make sure we're fully resumed: */
 	if (unlikely(timekeeping_suspended))
@@ -1205,8 +1223,8 @@ static void update_wall_time(void)
 	timekeeping_update(tk, false);
 
 out:
-	write_sequnlock_irqrestore(&tk->lock, flags);
-
+	write_seqcount_end(&tk->seq);
+	raw_spin_unlock_irqrestore(&tk->lock, flags);
 }
 
 /**
@@ -1253,13 +1271,13 @@ void get_monotonic_boottime(struct times
 	WARN_ON(timekeeping_suspended);
 
 	do {
-		seq = read_seqbegin(&tk->lock);
+		seq = read_seqcount_begin(&tk->seq);
 		ts->tv_sec = tk->xtime_sec;
 		nsec = timekeeping_get_ns(tk);
 		tomono = tk->wall_to_monotonic;
 		sleep = tk->total_sleep_time;
 
-	} while (read_seqretry(&tk->lock, seq));
+	} while (read_seqcount_retry(&tk->seq, seq));
 
 	ts->tv_sec += tomono.tv_sec + sleep.tv_sec;
 	ts->tv_nsec = 0;
@@ -1318,10 +1336,10 @@ struct timespec current_kernel_time(void
 	unsigned long seq;
 
 	do {
-		seq = read_seqbegin(&tk->lock);
+		seq = read_seqcount_begin(&tk->seq);
 
 		now = tk_xtime(tk);
-	} while (read_seqretry(&tk->lock, seq));
+	} while (read_seqcount_retry(&tk->seq, seq));
 
 	return now;
 }
@@ -1334,11 +1352,11 @@ struct timespec get_monotonic_coarse(voi
 	unsigned long seq;
 
 	do {
-		seq = read_seqbegin(&tk->lock);
+		seq = read_seqcount_begin(&tk->seq);
 
 		now = tk_xtime(tk);
 		mono = tk->wall_to_monotonic;
-	} while (read_seqretry(&tk->lock, seq));
+	} while (read_seqcount_retry(&tk->seq, seq));
 
 	set_normalized_timespec(&now, now.tv_sec + mono.tv_sec,
 				now.tv_nsec + mono.tv_nsec);
@@ -1371,11 +1389,11 @@ void get_xtime_and_monotonic_and_sleep_o
 	unsigned long seq;
 
 	do {
-		seq = read_seqbegin(&tk->lock);
+		seq = read_seqcount_begin(&tk->seq);
 		*xtim = tk_xtime(tk);
 		*wtom = tk->wall_to_monotonic;
 		*sleep = tk->total_sleep_time;
-	} while (read_seqretry(&tk->lock, seq));
+	} while (read_seqcount_retry(&tk->seq, seq));
 }
 
 #ifdef CONFIG_HIGH_RES_TIMERS
@@ -1395,14 +1413,14 @@ ktime_t ktime_get_update_offsets(ktime_t
 	u64 secs, nsecs;
 
 	do {
-		seq = read_seqbegin(&tk->lock);
+		seq = read_seqcount_begin(&tk->seq);
 
 		secs = tk->xtime_sec;
 		nsecs = timekeeping_get_ns(tk);
 
 		*offs_real = tk->offs_real;
 		*offs_boot = tk->offs_boot;
-	} while (read_seqretry(&tk->lock, seq));
+	} while (read_seqcount_retry(&tk->seq, seq));
 
 	now = ktime_add_ns(ktime_set(secs, 0), nsecs);
 	now = ktime_sub(now, *offs_real);
@@ -1420,9 +1438,9 @@ ktime_t ktime_get_monotonic_offset(void)
 	struct timespec wtom;
 
 	do {
-		seq = read_seqbegin(&tk->lock);
+		seq = read_seqcount_begin(&tk->seq);
 		wtom = tk->wall_to_monotonic;
-	} while (read_seqretry(&tk->lock, seq));
+	} while (read_seqcount_retry(&tk->seq, seq));
 
 	return timespec_to_ktime(wtom);
 }
@@ -1436,7 +1454,9 @@ EXPORT_SYMBOL_GPL(ktime_get_monotonic_of
  */
 void xtime_update(unsigned long ticks)
 {
-	write_seqlock(&xtime_lock);
+	raw_spin_lock(&xtime_lock);
+	write_seqcount_begin(&xtime_seq);
 	do_timer(ticks);
-	write_sequnlock(&xtime_lock);
+	write_seqcount_end(&xtime_seq);
+	raw_spin_unlock(&xtime_lock);
 }