Merge branch 'timers/core-v2' of git://git.kernel.org/pub/scm/linux/k…

…ernel/git/frederic/linux-dynticks into timers/core

Pull dynticks updates from Frederic Weisbecker:

  * Fix a bug where posix cpu timers requeued due to interval got ignored on full
    dynticks CPUs (not a regression though as it only impacts full dynticks and the
    bug is there since we merged full dynticks).

  * Optimizations and cleanups on the use of per CPU APIs to improve code readability,
    performance and debuggability in the nohz subsystem;

  * Optimize posix cpu timer by sparing stub workqueue queue with full dynticks off case

  * Rename some functions to extend with *_this_cpu() suffix for clarity

  * Refine the naming of some context tracking subsystem state accessors

  * Trivial spelling fix by Paul Gortmaker

Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/context_tracking.h

@@ -17,21 +17,21 @@ extern void __context_tracking_task_switch(struct task_struct *prev,
 
 static inline void user_enter(void)
 {
-	if (static_key_false(&context_tracking_enabled))
+	if (context_tracking_is_enabled())
 		context_tracking_user_enter();
 
 }
 static inline void user_exit(void)
 {
-	if (static_key_false(&context_tracking_enabled))
+	if (context_tracking_is_enabled())
 		context_tracking_user_exit();
 }
 
 static inline enum ctx_state exception_enter(void)
 {
 	enum ctx_state prev_ctx;
 
-	if (!static_key_false(&context_tracking_enabled))
+	if (!context_tracking_is_enabled())
 		return 0;
 
 	prev_ctx = this_cpu_read(context_tracking.state);
@@ -42,7 +42,7 @@ static inline enum ctx_state exception_enter(void)
 
 static inline void exception_exit(enum ctx_state prev_ctx)
 {
-	if (static_key_false(&context_tracking_enabled)) {
+	if (context_tracking_is_enabled()) {
 		if (prev_ctx == IN_USER)
 			context_tracking_user_enter();
 	}
@@ -51,7 +51,7 @@ static inline void exception_exit(enum ctx_state prev_ctx)
 static inline void context_tracking_task_switch(struct task_struct *prev,
 						struct task_struct *next)
 {
-	if (static_key_false(&context_tracking_enabled))
+	if (context_tracking_is_enabled())
 		__context_tracking_task_switch(prev, next);
 }
 #else

include/linux/context_tracking_state.h

@@ -22,15 +22,20 @@ struct context_tracking {
 extern struct static_key context_tracking_enabled;
 DECLARE_PER_CPU(struct context_tracking, context_tracking);
 
-static inline bool context_tracking_in_user(void)
+static inline bool context_tracking_is_enabled(void)
 {
-	return __this_cpu_read(context_tracking.state) == IN_USER;
+	return static_key_false(&context_tracking_enabled);
 }
 
-static inline bool context_tracking_active(void)
+static inline bool context_tracking_cpu_is_enabled(void)
 {
 	return __this_cpu_read(context_tracking.active);
 }
+
+static inline bool context_tracking_in_user(void)
+{
+	return __this_cpu_read(context_tracking.state) == IN_USER;
+}
 #else
 static inline bool context_tracking_in_user(void) { return false; }
 static inline bool context_tracking_active(void) { return false; }

include/linux/tick.h

@@ -104,15 +104,15 @@ extern struct cpumask *tick_get_broadcast_oneshot_mask(void);
 extern void tick_clock_notify(void);
 extern int tick_check_oneshot_change(int allow_nohz);
 extern struct tick_sched *tick_get_tick_sched(int cpu);
-extern void tick_check_idle(int cpu);
+extern void tick_check_idle(void);
 extern int tick_oneshot_mode_active(void);
 #  ifndef arch_needs_cpu
 #   define arch_needs_cpu(cpu) (0)
 #  endif
 # else
 static inline void tick_clock_notify(void) { }
 static inline int tick_check_oneshot_change(int allow_nohz) { return 0; }
-static inline void tick_check_idle(int cpu) { }
+static inline void tick_check_idle(void) { }
 static inline int tick_oneshot_mode_active(void) { return 0; }
 # endif
 
@@ -121,7 +121,7 @@ static inline void tick_init(void) { }
 static inline void tick_cancel_sched_timer(int cpu) { }
 static inline void tick_clock_notify(void) { }
 static inline int tick_check_oneshot_change(int allow_nohz) { return 0; }
-static inline void tick_check_idle(int cpu) { }
+static inline void tick_check_idle(void) { }
 static inline int tick_oneshot_mode_active(void) { return 0; }
 #endif /* !CONFIG_GENERIC_CLOCKEVENTS */
 
@@ -165,7 +165,7 @@ extern cpumask_var_t tick_nohz_full_mask;
 
 static inline bool tick_nohz_full_enabled(void)
 {
-	if (!static_key_false(&context_tracking_enabled))
+	if (!context_tracking_is_enabled())
 		return false;
 
 	return tick_nohz_full_running;

include/linux/vtime.h

@@ -19,8 +19,8 @@ static inline bool vtime_accounting_enabled(void) { return true; }
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
 static inline bool vtime_accounting_enabled(void)
 {
-	if (static_key_false(&context_tracking_enabled)) {
-		if (context_tracking_active())
+	if (context_tracking_is_enabled()) {
+		if (context_tracking_cpu_is_enabled())
 			return true;
 	}
 

init/Kconfig

@@ -532,7 +532,7 @@ config CONTEXT_TRACKING_FORCE
 	  dynticks subsystem by forcing the context tracking on all
 	  CPUs in the system.
 
-	  Say Y only if you're working on the developpement of an
+	  Say Y only if you're working on the development of an
 	  architecture backend for the context tracking.
 
 	  Say N otherwise, this option brings an overhead that you

kernel/context_tracking.c

@@ -53,10 +53,10 @@ void context_tracking_user_enter(void)
 	/*
 	 * Repeat the user_enter() check here because some archs may be calling
 	 * this from asm and if no CPU needs context tracking, they shouldn't
-	 * go further. Repeat the check here until they support the static key
-	 * check.
+	 * go further. Repeat the check here until they support the inline static
+	 * key check.
 	 */
-	if (!static_key_false(&context_tracking_enabled))
+	if (!context_tracking_is_enabled())
 		return;
 
 	/*
@@ -160,7 +160,7 @@ void context_tracking_user_exit(void)
 {
 	unsigned long flags;
 
-	if (!static_key_false(&context_tracking_enabled))
+	if (!context_tracking_is_enabled())
 		return;
 
 	if (in_interrupt())

kernel/posix-cpu-timers.c

@@ -608,7 +608,8 @@ static DECLARE_WORK(nohz_kick_work, nohz_kick_work_fn);
  */
 static void posix_cpu_timer_kick_nohz(void)
 {
-	schedule_work(&nohz_kick_work);
+	if (context_tracking_is_enabled())
+		schedule_work(&nohz_kick_work);
 }
 
 bool posix_cpu_timers_can_stop_tick(struct task_struct *tsk)
@@ -1090,7 +1091,8 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
 			put_task_struct(p);
 			timer->it.cpu.task = p = NULL;
 			timer->it.cpu.expires = 0;
-			goto out_unlock;
+			read_unlock(&tasklist_lock);
+			goto out;
 		} else if (unlikely(p->exit_state) && thread_group_empty(p)) {
 			/*
 			 * We've noticed that the thread is dead, but
@@ -1099,7 +1101,8 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
 			 */
 			cpu_timer_sample_group(timer->it_clock, p, &now);
 			clear_dead_task(timer, now);
-			goto out_unlock;
+			read_unlock(&tasklist_lock);
+			goto out;
 		}
 		spin_lock(&p->sighand->siglock);
 		cpu_timer_sample_group(timer->it_clock, p, &now);
@@ -1113,10 +1116,11 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
 	BUG_ON(!irqs_disabled());
 	arm_timer(timer);
 	spin_unlock(&p->sighand->siglock);
-
-out_unlock:
 	read_unlock(&tasklist_lock);
 
+	/* Kick full dynticks CPUs in case they need to tick on the new timer */
+	posix_cpu_timer_kick_nohz();
+
 out:
 	timer->it_overrun_last = timer->it_overrun;
 	timer->it_overrun = -1;
@@ -1256,13 +1260,6 @@ void run_posix_cpu_timers(struct task_struct *tsk)
 			cpu_timer_fire(timer);
 		spin_unlock(&timer->it_lock);
 	}
-
-	/*
-	 * In case some timers were rescheduled after the queue got emptied,
-	 * wake up full dynticks CPUs.
-	 */
-	if (tsk->signal->cputimer.running)
-		posix_cpu_timer_kick_nohz();
 }
 
 /*

kernel/softirq.c

@@ -311,16 +311,14 @@ asmlinkage void do_softirq(void)
  */
 void irq_enter(void)
 {
-	int cpu = smp_processor_id();
-
 	rcu_irq_enter();
 	if (is_idle_task(current) && !in_interrupt()) {
 		/*
 		 * Prevent raise_softirq from needlessly waking up ksoftirqd
 		 * here, as softirq will be serviced on return from interrupt.
 		 */
 		local_bh_disable();
-		tick_check_idle(cpu);
+		tick_check_idle();
 		_local_bh_enable();
 	}
 

kernel/time/tick-broadcast.c

@@ -538,10 +538,10 @@ int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
  * Called from irq_enter() when idle was interrupted to reenable the
  * per cpu device.
  */
-void tick_check_oneshot_broadcast(int cpu)
+void tick_check_oneshot_broadcast_this_cpu(void)
 {
-	if (cpumask_test_cpu(cpu, tick_broadcast_oneshot_mask)) {
-		struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
+	if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) {
+		struct tick_device *td = &__get_cpu_var(tick_cpu_device);
 
 		/*
 		 * We might be in the middle of switching over from

kernel/time/tick-internal.h

@@ -51,7 +51,7 @@ extern void tick_broadcast_switch_to_oneshot(void);
 extern void tick_shutdown_broadcast_oneshot(unsigned int *cpup);
 extern int tick_resume_broadcast_oneshot(struct clock_event_device *bc);
 extern int tick_broadcast_oneshot_active(void);
-extern void tick_check_oneshot_broadcast(int cpu);
+extern void tick_check_oneshot_broadcast_this_cpu(void);
 bool tick_broadcast_oneshot_available(void);
 # else /* BROADCAST */
 static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
@@ -62,7 +62,7 @@ static inline void tick_broadcast_oneshot_control(unsigned long reason) { }
 static inline void tick_broadcast_switch_to_oneshot(void) { }
 static inline void tick_shutdown_broadcast_oneshot(unsigned int *cpup) { }
 static inline int tick_broadcast_oneshot_active(void) { return 0; }
-static inline void tick_check_oneshot_broadcast(int cpu) { }
+static inline void tick_check_oneshot_broadcast_this_cpu(void) { }
 static inline bool tick_broadcast_oneshot_available(void) { return true; }
 # endif /* !BROADCAST */
 

kernel/time/tick-sched.c

@@ -391,11 +391,9 @@ __setup("nohz=", setup_tick_nohz);
  */
 static void tick_nohz_update_jiffies(ktime_t now)
 {
-	int cpu = smp_processor_id();
-	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
 	unsigned long flags;
 
-	ts->idle_waketime = now;
+	__this_cpu_write(tick_cpu_sched.idle_waketime, now);
 
 	local_irq_save(flags);
 	tick_do_update_jiffies64(now);
@@ -426,17 +424,15 @@ update_ts_time_stats(int cpu, struct tick_sched *ts, ktime_t now, u64 *last_upda
 
 }
 
-static void tick_nohz_stop_idle(int cpu, ktime_t now)
+static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now)
 {
-	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
-
-	update_ts_time_stats(cpu, ts, now, NULL);
+	update_ts_time_stats(smp_processor_id(), ts, now, NULL);
 	ts->idle_active = 0;
 
 	sched_clock_idle_wakeup_event(0);
 }
 
-static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts)
+static ktime_t tick_nohz_start_idle(struct tick_sched *ts)
 {
 	ktime_t now = ktime_get();
 
@@ -752,7 +748,7 @@ static void __tick_nohz_idle_enter(struct tick_sched *ts)
 	ktime_t now, expires;
 	int cpu = smp_processor_id();
 
-	now = tick_nohz_start_idle(cpu, ts);
+	now = tick_nohz_start_idle(ts);
 
 	if (can_stop_idle_tick(cpu, ts)) {
 		int was_stopped = ts->tick_stopped;
@@ -914,8 +910,7 @@ static void tick_nohz_account_idle_ticks(struct tick_sched *ts)
  */
 void tick_nohz_idle_exit(void)
 {
-	int cpu = smp_processor_id();
-	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+	struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
 	ktime_t now;
 
 	local_irq_disable();
@@ -928,7 +923,7 @@ void tick_nohz_idle_exit(void)
 		now = ktime_get();
 
 	if (ts->idle_active)
-		tick_nohz_stop_idle(cpu, now);
+		tick_nohz_stop_idle(ts, now);
 
 	if (ts->tick_stopped) {
 		tick_nohz_restart_sched_tick(ts, now);
@@ -1012,12 +1007,10 @@ static void tick_nohz_switch_to_nohz(void)
  * timer and do not touch the other magic bits which need to be done
  * when idle is left.
  */
-static void tick_nohz_kick_tick(int cpu, ktime_t now)
+static void tick_nohz_kick_tick(struct tick_sched *ts, ktime_t now)
 {
 #if 0
 	/* Switch back to 2.6.27 behaviour */
-
-	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
 	ktime_t delta;
 
 	/*
@@ -1032,36 +1025,36 @@ static void tick_nohz_kick_tick(int cpu, ktime_t now)
 #endif
 }
 
-static inline void tick_check_nohz(int cpu)
+static inline void tick_check_nohz_this_cpu(void)
 {
-	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+	struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
 	ktime_t now;
 
 	if (!ts->idle_active && !ts->tick_stopped)
 		return;
 	now = ktime_get();
 	if (ts->idle_active)
-		tick_nohz_stop_idle(cpu, now);
+		tick_nohz_stop_idle(ts, now);
 	if (ts->tick_stopped) {
 		tick_nohz_update_jiffies(now);
-		tick_nohz_kick_tick(cpu, now);
+		tick_nohz_kick_tick(ts, now);
 	}
 }
 
 #else
 
 static inline void tick_nohz_switch_to_nohz(void) { }
-static inline void tick_check_nohz(int cpu) { }
+static inline void tick_check_nohz_this_cpu(void) { }
 
 #endif /* CONFIG_NO_HZ_COMMON */
 
 /*
  * Called from irq_enter to notify about the possible interruption of idle()
  */
-void tick_check_idle(int cpu)
+void tick_check_idle(void)
 {
-	tick_check_oneshot_broadcast(cpu);
-	tick_check_nohz(cpu);
+	tick_check_oneshot_broadcast_this_cpu();
+	tick_check_nohz_this_cpu();
 }
 
 /*