path: root/patches/0012-timekeeping-Split-xtime_lock.patch

From dcdd46d4ecb73da356e8bb29f315988f30df5193 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 1 Mar 2012 15:14:06 +0100
Subject: [PATCH 012/271] timekeeping: Split xtime_lock

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   |  114 +++++++++++++++++++++++++------------------
 5 files changed, 87 insertions(+), 60 deletions(-)

diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c
index a470154..21940eb 100644
--- a/kernel/time/jiffies.c
+++ b/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);
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index da6c9ec..39de540 100644
--- a/kernel/time/tick-common.c
+++ b/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_event_device *dev, int broadcast)
 		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);
 
diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index 4e265b9..c91100d 100644
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -141,4 +141,5 @@ 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;
+extern raw_spinlock_t xtime_lock;
+extern seqcount_t xtime_seq;
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 2a8766c..d81185f 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -56,7 +56,8 @@ static void tick_do_update_jiffies64(ktime_t now)
 		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(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_seqcount_end(&xtime_seq);
+	raw_spin_unlock(&xtime_lock);
 }
 
 /*
@@ -89,12 +91,14 @@ static ktime_t tick_init_jiffy_update(void)
 {
 	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;
 }
 
@@ -317,11 +321,11 @@ static void tick_nohz_stop_sched_tick(struct tick_sched *ts)
 	ts->idle_calls++;
 	/* 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) || printk_needs_cpu(cpu) ||
 	    arch_needs_cpu(cpu)) {
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 12843e9..f4e5eaf 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -76,8 +76,9 @@ struct timekeeper {
 	/* Offset clock monotonic -> clock boottime */
 	ktime_t offs_boot;
 
-	/* Seqlock for all timekeeper values */
-	seqlock_t lock;
+	/* Open coded seqlock for all timekeeper values */
+	seqcount_t seq;
+	raw_spinlock_t lock;
 };
 
 static struct timekeeper timekeeper;
@@ -86,7 +87,8 @@ 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 */
@@ -243,7 +245,7 @@ void getnstimeofday(struct timespec *ts)
 	WARN_ON(timekeeping_suspended);
 
 	do {
-		seq = read_seqbegin(&timekeeper.lock);
+		seq = read_seqcount_begin(&timekeeper.seq);
 
 		*ts = timekeeper.xtime;
 		nsecs = timekeeping_get_ns();
@@ -251,7 +253,7 @@ void getnstimeofday(struct timespec *ts)
 		/* If arch requires, add in gettimeoffset() */
 		nsecs += arch_gettimeoffset();
 
-	} while (read_seqretry(&timekeeper.lock, seq));
+	} while (read_seqcount_retry(&timekeeper.seq, seq));
 
 	timespec_add_ns(ts, nsecs);
 }
@@ -266,7 +268,7 @@ ktime_t ktime_get(void)
 	WARN_ON(timekeeping_suspended);
 
 	do {
-		seq = read_seqbegin(&timekeeper.lock);
+		seq = read_seqcount_begin(&timekeeper.seq);
 		secs = timekeeper.xtime.tv_sec +
 				timekeeper.wall_to_monotonic.tv_sec;
 		nsecs = timekeeper.xtime.tv_nsec +
@@ -275,7 +277,7 @@ ktime_t ktime_get(void)
 		/* If arch requires, add in gettimeoffset() */
 		nsecs += arch_gettimeoffset();
 
-	} while (read_seqretry(&timekeeper.lock, seq));
+	} while (read_seqcount_retry(&timekeeper.seq, seq));
 	/*
 	 * Use ktime_set/ktime_add_ns to create a proper ktime on
 	 * 32-bit architectures without CONFIG_KTIME_SCALAR.
@@ -301,14 +303,14 @@ void ktime_get_ts(struct timespec *ts)
 	WARN_ON(timekeeping_suspended);
 
 	do {
-		seq = read_seqbegin(&timekeeper.lock);
+		seq = read_seqcount_begin(&timekeeper.seq);
 		*ts = timekeeper.xtime;
 		tomono = timekeeper.wall_to_monotonic;
 		nsecs = timekeeping_get_ns();
 		/* If arch requires, add in gettimeoffset() */
 		nsecs += arch_gettimeoffset();
 
-	} while (read_seqretry(&timekeeper.lock, seq));
+	} while (read_seqcount_retry(&timekeeper.seq, seq));
 
 	set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
 				ts->tv_nsec + tomono.tv_nsec + nsecs);
@@ -336,7 +338,7 @@ void getnstime_raw_and_real(struct timespec *ts_raw, struct timespec *ts_real)
 	do {
 		u32 arch_offset;
 
-		seq = read_seqbegin(&timekeeper.lock);
+		seq = read_seqcount_begin(&timekeeper.seq);
 
 		*ts_raw = timekeeper.raw_time;
 		*ts_real = timekeeper.xtime;
@@ -349,7 +351,7 @@ void getnstime_raw_and_real(struct timespec *ts_raw, struct timespec *ts_real)
 		nsecs_raw += arch_offset;
 		nsecs_real += arch_offset;
 
-	} while (read_seqretry(&timekeeper.lock, seq));
+	} while (read_seqcount_retry(&timekeeper.seq, seq));
 
 	timespec_add_ns(ts_raw, nsecs_raw);
 	timespec_add_ns(ts_real, nsecs_real);
@@ -388,7 +390,8 @@ int do_settimeofday(const struct timespec *tv)
 	if (!timespec_valid_strict(tv))
 		return -EINVAL;
 
-	write_seqlock_irqsave(&timekeeper.lock, flags);
+	raw_spin_lock_irqsave(&timekeeper.lock, flags);
+	write_seqcount_begin(&timekeeper.seq);
 
 	timekeeping_forward_now();
 
@@ -400,7 +403,8 @@ int do_settimeofday(const struct timespec *tv)
 	timekeeper.xtime = *tv;
 	timekeeping_update(true);
 
-	write_sequnlock_irqrestore(&timekeeper.lock, flags);
+	write_seqcount_end(&timekeeper.seq);
+	raw_spin_unlock_irqrestore(&timekeeper.lock, flags);
 
 	/* signal hrtimers about time change */
 	clock_was_set();
@@ -426,7 +430,8 @@ int timekeeping_inject_offset(struct timespec *ts)
 	if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC)
 		return -EINVAL;
 
-	write_seqlock_irqsave(&timekeeper.lock, flags);
+	raw_spin_lock_irqsave(&timekeeper.lock, flags);
+	write_seqcount_begin(&timekeeper.seq);
 
 	timekeeping_forward_now();
 
@@ -443,7 +448,8 @@ int timekeeping_inject_offset(struct timespec *ts)
 error: /* even if we error out, we forwarded the time, so call update */
 	timekeeping_update(true);
 
-	write_sequnlock_irqrestore(&timekeeper.lock, flags);
+	write_seqcount_end(&timekeeper.seq);
+	raw_spin_unlock_irqrestore(&timekeeper.lock, flags);
 
 	/* signal hrtimers about time change */
 	clock_was_set();
@@ -464,7 +470,8 @@ static int change_clocksource(void *data)
 
 	new = (struct clocksource *) data;
 
-	write_seqlock_irqsave(&timekeeper.lock, flags);
+	raw_spin_lock_irqsave(&timekeeper.lock, flags);
+	write_seqcount_begin(&timekeeper.seq);
 
 	timekeeping_forward_now();
 	if (!new->enable || new->enable(new) == 0) {
@@ -475,7 +482,8 @@ static int change_clocksource(void *data)
 	}
 	timekeeping_update(true);
 
-	write_sequnlock_irqrestore(&timekeeper.lock, flags);
+	write_seqcount_end(&timekeeper.seq);
+	raw_spin_unlock_irqrestore(&timekeeper.lock, flags);
 
 	return 0;
 }
@@ -522,11 +530,11 @@ void getrawmonotonic(struct timespec *ts)
 	s64 nsecs;
 
 	do {
-		seq = read_seqbegin(&timekeeper.lock);
+		seq = read_seqcount_begin(&timekeeper.seq);
 		nsecs = timekeeping_get_ns_raw();
 		*ts = timekeeper.raw_time;
 
-	} while (read_seqretry(&timekeeper.lock, seq));
+	} while (read_seqcount_retry(&timekeeper.seq, seq));
 
 	timespec_add_ns(ts, nsecs);
 }
@@ -542,11 +550,11 @@ int timekeeping_valid_for_hres(void)
 	int ret;
 
 	do {
-		seq = read_seqbegin(&timekeeper.lock);
+		seq = read_seqcount_begin(&timekeeper.seq);
 
 		ret = timekeeper.clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
 
-	} while (read_seqretry(&timekeeper.lock, seq));
+	} while (read_seqcount_retry(&timekeeper.seq, seq));
 
 	return ret;
 }
@@ -559,11 +567,11 @@ u64 timekeeping_max_deferment(void)
 	unsigned long seq;
 	u64 ret;
 	do {
-		seq = read_seqbegin(&timekeeper.lock);
+		seq = read_seqcount_begin(&timekeeper.seq);
 
 		ret = timekeeper.clock->max_idle_ns;
 
-	} while (read_seqretry(&timekeeper.lock, seq));
+	} while (read_seqcount_retry(&timekeeper.seq, seq));
 
 	return ret;
 }
@@ -623,11 +631,13 @@ void __init timekeeping_init(void)
 		boot.tv_nsec = 0;
 	}
 
-	seqlock_init(&timekeeper.lock);
+	raw_spin_lock_init(&timekeeper.lock);
+	seqcount_init(&timekeeper.seq);
 
 	ntp_init();
 
-	write_seqlock_irqsave(&timekeeper.lock, flags);
+	raw_spin_lock_irqsave(&timekeeper.lock, flags);
+	write_seqcount_begin(&timekeeper.seq);
 	clock = clocksource_default_clock();
 	if (clock->enable)
 		clock->enable(clock);
@@ -646,7 +656,8 @@ void __init timekeeping_init(void)
 	update_rt_offset();
 	timekeeper.total_sleep_time.tv_sec = 0;
 	timekeeper.total_sleep_time.tv_nsec = 0;
-	write_sequnlock_irqrestore(&timekeeper.lock, flags);
+	write_seqcount_end(&timekeeper.seq);
+	raw_spin_unlock_irqrestore(&timekeeper.lock, flags);
 }
 
 /* time in seconds when suspend began */
@@ -700,7 +711,8 @@ void timekeeping_inject_sleeptime(struct timespec *delta)
 	if (!(ts.tv_sec == 0 && ts.tv_nsec == 0))
 		return;
 
-	write_seqlock_irqsave(&timekeeper.lock, flags);
+	raw_spin_lock_irqsave(&timekeeper.lock, flags);
+	write_seqcount_begin(&timekeeper.seq);
 
 	timekeeping_forward_now();
 
@@ -708,7 +720,8 @@ void timekeeping_inject_sleeptime(struct timespec *delta)
 
 	timekeeping_update(true);
 
-	write_sequnlock_irqrestore(&timekeeper.lock, flags);
+	write_seqcount_end(&timekeeper.seq);
+	raw_spin_unlock_irqrestore(&timekeeper.lock, flags);
 
 	/* signal hrtimers about time change */
 	clock_was_set();
@@ -731,7 +744,8 @@ static void timekeeping_resume(void)
 
 	clocksource_resume();
 
-	write_seqlock_irqsave(&timekeeper.lock, flags);
+	raw_spin_lock_irqsave(&timekeeper.lock, flags);
+	write_seqcount_begin(&timekeeper.seq);
 
 	if (timespec_compare(&ts, &timekeeping_suspend_time) > 0) {
 		ts = timespec_sub(ts, timekeeping_suspend_time);
@@ -742,7 +756,8 @@ static void timekeeping_resume(void)
 	timekeeper.ntp_error = 0;
 	timekeeping_suspended = 0;
 	timekeeping_update(false);
-	write_sequnlock_irqrestore(&timekeeper.lock, flags);
+	write_seqcount_end(&timekeeper.seq);
+	raw_spin_unlock_irqrestore(&timekeeper.lock, flags);
 
 	touch_softlockup_watchdog();
 
@@ -760,7 +775,8 @@ static int timekeeping_suspend(void)
 
 	read_persistent_clock(&timekeeping_suspend_time);
 
-	write_seqlock_irqsave(&timekeeper.lock, flags);
+	raw_spin_lock_irqsave(&timekeeper.lock, flags);
+	write_seqcount_begin(&timekeeper.seq);
 	timekeeping_forward_now();
 	timekeeping_suspended = 1;
 
@@ -783,7 +799,8 @@ static int timekeeping_suspend(void)
 		timekeeping_suspend_time =
 			timespec_add(timekeeping_suspend_time, delta_delta);
 	}
-	write_sequnlock_irqrestore(&timekeeper.lock, flags);
+	write_seqcount_end(&timekeeper.seq);
+	raw_spin_unlock_irqrestore(&timekeeper.lock, flags);
 
 	clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
 	clocksource_suspend();
@@ -1044,7 +1061,8 @@ static void update_wall_time(void)
 	int shift = 0, maxshift;
 	unsigned long flags;
 
-	write_seqlock_irqsave(&timekeeper.lock, flags);
+	raw_spin_lock_irqsave(&timekeeper.lock, flags);
+	write_seqcount_begin(&timekeeper.seq);
 
 	/* Make sure we're fully resumed: */
 	if (unlikely(timekeeping_suspended))
@@ -1137,8 +1155,8 @@ static void update_wall_time(void)
 	timekeeping_update(false);
 
 out:
-	write_sequnlock_irqrestore(&timekeeper.lock, flags);
-
+	write_seqcount_end(&timekeeper.seq);
+	raw_spin_unlock_irqrestore(&timekeeper.lock, flags);
 }
 
 /**
@@ -1184,13 +1202,13 @@ void get_monotonic_boottime(struct timespec *ts)
 	WARN_ON(timekeeping_suspended);
 
 	do {
-		seq = read_seqbegin(&timekeeper.lock);
+		seq = read_seqcount_begin(&timekeeper.seq);
 		*ts = timekeeper.xtime;
 		tomono = timekeeper.wall_to_monotonic;
 		sleep = timekeeper.total_sleep_time;
 		nsecs = timekeeping_get_ns();
 
-	} while (read_seqretry(&timekeeper.lock, seq));
+	} while (read_seqcount_retry(&timekeeper.seq, seq));
 
 	set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec + sleep.tv_sec,
 			ts->tv_nsec + tomono.tv_nsec + sleep.tv_nsec + nsecs);
@@ -1241,10 +1259,10 @@ struct timespec current_kernel_time(void)
 	unsigned long seq;
 
 	do {
-		seq = read_seqbegin(&timekeeper.lock);
+		seq = read_seqcount_begin(&timekeeper.seq);
 
 		now = timekeeper.xtime;
-	} while (read_seqretry(&timekeeper.lock, seq));
+	} while (read_seqcount_retry(&timekeeper.seq, seq));
 
 	return now;
 }
@@ -1256,11 +1274,11 @@ struct timespec get_monotonic_coarse(void)
 	unsigned long seq;
 
 	do {
-		seq = read_seqbegin(&timekeeper.lock);
+		seq = read_seqcount_begin(&timekeeper.seq);
 
 		now = timekeeper.xtime;
 		mono = timekeeper.wall_to_monotonic;
-	} while (read_seqretry(&timekeeper.lock, seq));
+	} while (read_seqcount_retry(&timekeeper.seq, seq));
 
 	set_normalized_timespec(&now, now.tv_sec + mono.tv_sec,
 				now.tv_nsec + mono.tv_nsec);
@@ -1292,11 +1310,11 @@ void get_xtime_and_monotonic_and_sleep_offset(struct timespec *xtim,
 	unsigned long seq;
 
 	do {
-		seq = read_seqbegin(&timekeeper.lock);
+		seq = read_seqcount_begin(&timekeeper.seq);
 		*xtim = timekeeper.xtime;
 		*wtom = timekeeper.wall_to_monotonic;
 		*sleep = timekeeper.total_sleep_time;
-	} while (read_seqretry(&timekeeper.lock, seq));
+	} while (read_seqcount_retry(&timekeeper.seq, seq));
 }
 
 #ifdef CONFIG_HIGH_RES_TIMERS
@@ -1342,9 +1360,9 @@ ktime_t ktime_get_monotonic_offset(void)
 	struct timespec wtom;
 
 	do {
-		seq = read_seqbegin(&timekeeper.lock);
+		seq = read_seqcount_begin(&timekeeper.seq);
 		wtom = timekeeper.wall_to_monotonic;
-	} while (read_seqretry(&timekeeper.lock, seq));
+	} while (read_seqcount_retry(&timekeeper.seq, seq));
 
 	return timespec_to_ktime(wtom);
 }
@@ -1359,7 +1377,9 @@ EXPORT_SYMBOL_GPL(ktime_get_monotonic_offset);
  */
 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);
 }
-- 
1.7.10.4