Message-ID: <20150831172909.GA6707@gmail.com>
Date:	Mon, 31 Aug 2015 19:29:09 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [GIT PULL] NOHZ updates for v4.3

Linus,

Please pull the latest timers-nohz-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers-nohz-for-linus

   # HEAD: 555ee95a0a5a525ad2f1654fab0bd157de832b4f Merge branch 'timers/nohz-for-tip' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks into timers/nohz


The main changes, mostly written by Frederic Weisbecker, include:

      - Fix some jiffies based cputime assumptions. (No real harm because the
        concerned code isn't used by full dynticks.)
    
      - Simplify jiffies <-> usecs conversions. Remove dead code.
   
      - Remove early hacks on nohz full code that avoided messing up idle
        nohz internals. Now nohz integrates well full and idle and such hack
        have become needless.
    
      - Restart nohz full tick from irq exit. (A simplification and a
        preparation for future optimization on scheduler kick to nohz full.)
    
      - Code cleanups.
    
      - Tile driver isolation enhancement on top of nohz. (Chris Metcalf)

 Thanks,

	Ingo

------------------>
Chris Metcalf (1):
      nohz: Prevent tilegx network driver interrupts

Frederic Weisbecker (7):
      jiffies: Remove HZ > USEC_PER_SEC special case
      apm32: Fix cputime == jiffies assumption
      alpha: Fix jiffies based cputime assumption
      nohz: Remove idle task special case
      nohz: Restart nohz full tick from irq exit
      nohz: Move tick_nohz_restart_sched_tick() above its users
      nohz: Remove useless argument on tick_nohz_task_switch()


 arch/alpha/kernel/osf_sys.c        | 13 ++++---
 arch/x86/kernel/apm_32.c           |  2 +-
 drivers/net/ethernet/tile/tilegx.c |  4 ++-
 include/linux/jiffies.h            |  9 +----
 include/linux/tick.h               | 25 ++++++-------
 kernel/sched/core.c                |  2 +-
 kernel/time/tick-sched.c           | 72 ++++++++++++++------------------------
 kernel/time/time.c                 | 10 ++++--
 8 files changed, 62 insertions(+), 75 deletions(-)

diff --git a/arch/alpha/kernel/osf_sys.c b/arch/alpha/kernel/osf_sys.c
index 36dc91ace83a..6cc08166ff00 100644
--- a/arch/alpha/kernel/osf_sys.c
+++ b/arch/alpha/kernel/osf_sys.c
@@ -1138,6 +1138,7 @@ SYSCALL_DEFINE2(osf_getrusage, int, who, struct rusage32 __user *, ru)
 {
 	struct rusage32 r;
 	cputime_t utime, stime;
+	unsigned long utime_jiffies, stime_jiffies;
 
 	if (who != RUSAGE_SELF && who != RUSAGE_CHILDREN)
 		return -EINVAL;
@@ -1146,14 +1147,18 @@ SYSCALL_DEFINE2(osf_getrusage, int, who, struct rusage32 __user *, ru)
 	switch (who) {
 	case RUSAGE_SELF:
 		task_cputime(current, &utime, &stime);
-		jiffies_to_timeval32(utime, &r.ru_utime);
-		jiffies_to_timeval32(stime, &r.ru_stime);
+		utime_jiffies = cputime_to_jiffies(utime);
+		stime_jiffies = cputime_to_jiffies(stime);
+		jiffies_to_timeval32(utime_jiffies, &r.ru_utime);
+		jiffies_to_timeval32(stime_jiffies, &r.ru_stime);
 		r.ru_minflt = current->min_flt;
 		r.ru_majflt = current->maj_flt;
 		break;
 	case RUSAGE_CHILDREN:
-		jiffies_to_timeval32(current->signal->cutime, &r.ru_utime);
-		jiffies_to_timeval32(current->signal->cstime, &r.ru_stime);
+		utime_jiffies = cputime_to_jiffies(current->signal->cutime);
+		stime_jiffies = cputime_to_jiffies(current->signal->cstime);
+		jiffies_to_timeval32(utime_jiffies, &r.ru_utime);
+		jiffies_to_timeval32(stime_jiffies, &r.ru_stime);
 		r.ru_minflt = current->signal->cmin_flt;
 		r.ru_majflt = current->signal->cmaj_flt;
 		break;
diff --git a/arch/x86/kernel/apm_32.c b/arch/x86/kernel/apm_32.c
index 927ec9235947..052c9c3026cc 100644
--- a/arch/x86/kernel/apm_32.c
+++ b/arch/x86/kernel/apm_32.c
@@ -919,7 +919,7 @@ static int apm_cpu_idle(struct cpuidle_device *dev,
 	} else if (jiffies_since_last_check > idle_period) {
 		unsigned int idle_percentage;
 
-		idle_percentage = stime - last_stime;
+		idle_percentage = cputime_to_jiffies(stime - last_stime);
 		idle_percentage *= 100;
 		idle_percentage /= jiffies_since_last_check;
 		use_apm_idle = (idle_percentage > idle_threshold);
diff --git a/drivers/net/ethernet/tile/tilegx.c b/drivers/net/ethernet/tile/tilegx.c
index a3f7610002aa..0a15acc075b3 100644
--- a/drivers/net/ethernet/tile/tilegx.c
+++ b/drivers/net/ethernet/tile/tilegx.c
@@ -40,6 +40,7 @@
 #include <linux/tcp.h>
 #include <linux/net_tstamp.h>
 #include <linux/ptp_clock_kernel.h>
+#include <linux/tick.h>
 
 #include <asm/checksum.h>
 #include <asm/homecache.h>
@@ -2273,7 +2274,8 @@ static int __init tile_net_init_module(void)
 		tile_net_dev_init(name, mac);
 
 	if (!network_cpus_init())
-		network_cpus_map = *cpu_online_mask;
+		cpumask_and(&network_cpus_map, housekeeping_cpumask(),
+			    cpu_online_mask);
 
 	return 0;
 }
diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h
index 535fd3bb1ba8..7c6febede6ba 100644
--- a/include/linux/jiffies.h
+++ b/include/linux/jiffies.h
@@ -363,18 +363,11 @@ static inline unsigned long msecs_to_jiffies(const unsigned int m)
 }
 
 extern unsigned long __usecs_to_jiffies(const unsigned int u);
-#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
+#if !(USEC_PER_SEC % HZ)
 static inline unsigned long _usecs_to_jiffies(const unsigned int u)
 {
 	return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
 }
-#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
-static inline unsigned long _usecs_to_jiffies(const unsigned int u)
-{
-	return u * (HZ / USEC_PER_SEC);
-}
-static inline unsigned long _usecs_to_jiffies(const unsigned int u)
-{
 #else
 static inline unsigned long _usecs_to_jiffies(const unsigned int u)
 {
diff --git a/include/linux/tick.h b/include/linux/tick.h
index edbfc9a5293e..48d901f83f92 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -147,22 +147,29 @@ static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask)
 		cpumask_or(mask, mask, tick_nohz_full_mask);
 }
 
-extern void __tick_nohz_full_check(void);
 extern void tick_nohz_full_kick(void);
 extern void tick_nohz_full_kick_cpu(int cpu);
 extern void tick_nohz_full_kick_all(void);
-extern void __tick_nohz_task_switch(struct task_struct *tsk);
+extern void __tick_nohz_task_switch(void);
 #else
 static inline bool tick_nohz_full_enabled(void) { return false; }
 static inline bool tick_nohz_full_cpu(int cpu) { return false; }
 static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask) { }
-static inline void __tick_nohz_full_check(void) { }
 static inline void tick_nohz_full_kick_cpu(int cpu) { }
 static inline void tick_nohz_full_kick(void) { }
 static inline void tick_nohz_full_kick_all(void) { }
-static inline void __tick_nohz_task_switch(struct task_struct *tsk) { }
+static inline void __tick_nohz_task_switch(void) { }
 #endif
 
+static inline const struct cpumask *housekeeping_cpumask(void)
+{
+#ifdef CONFIG_NO_HZ_FULL
+	if (tick_nohz_full_enabled())
+		return housekeeping_mask;
+#endif
+	return cpu_possible_mask;
+}
+
 static inline bool is_housekeeping_cpu(int cpu)
 {
 #ifdef CONFIG_NO_HZ_FULL
@@ -181,16 +188,10 @@ static inline void housekeeping_affine(struct task_struct *t)
 #endif
 }
 
-static inline void tick_nohz_full_check(void)
-{
-	if (tick_nohz_full_enabled())
-		__tick_nohz_full_check();
-}
-
-static inline void tick_nohz_task_switch(struct task_struct *tsk)
+static inline void tick_nohz_task_switch(void)
 {
 	if (tick_nohz_full_enabled())
-		__tick_nohz_task_switch(tsk);
+		__tick_nohz_task_switch();
 }
 
 #endif
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 78b4bad10081..4d34035bb3ee 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2489,7 +2489,7 @@ static struct rq *finish_task_switch(struct task_struct *prev)
 		put_task_struct(prev);
 	}
 
-	tick_nohz_task_switch(current);
+	tick_nohz_task_switch();
 	return rq;
 }
 
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index c792429e98c6..3319e16f31e5 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -197,27 +197,9 @@ static bool can_stop_full_tick(void)
 	return true;
 }
 
-static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now);
-
-/*
- * Re-evaluate the need for the tick on the current CPU
- * and restart it if necessary.
- */
-void __tick_nohz_full_check(void)
-{
-	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
-
-	if (tick_nohz_full_cpu(smp_processor_id())) {
-		if (ts->tick_stopped && !is_idle_task(current)) {
-			if (!can_stop_full_tick())
-				tick_nohz_restart_sched_tick(ts, ktime_get());
-		}
-	}
-}
-
 static void nohz_full_kick_work_func(struct irq_work *work)
 {
-	__tick_nohz_full_check();
+	/* Empty, the tick restart happens on tick_nohz_irq_exit() */
 }
 
 static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
@@ -252,7 +234,7 @@ void tick_nohz_full_kick_cpu(int cpu)
 
 static void nohz_full_kick_ipi(void *info)
 {
-	__tick_nohz_full_check();
+	/* Empty, the tick restart happens on tick_nohz_irq_exit() */
 }
 
 /*
@@ -276,7 +258,7 @@ void tick_nohz_full_kick_all(void)
  * It might need the tick due to per task/process properties:
  * perf events, posix cpu timers, ...
  */
-void __tick_nohz_task_switch(struct task_struct *tsk)
+void __tick_nohz_task_switch(void)
 {
 	unsigned long flags;
 
@@ -705,21 +687,38 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
 	return tick;
 }
 
-static void tick_nohz_full_stop_tick(struct tick_sched *ts)
+static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
+{
+	/* Update jiffies first */
+	tick_do_update_jiffies64(now);
+	update_cpu_load_nohz();
+
+	calc_load_exit_idle();
+	touch_softlockup_watchdog();
+	/*
+	 * Cancel the scheduled timer and restore the tick
+	 */
+	ts->tick_stopped  = 0;
+	ts->idle_exittime = now;
+
+	tick_nohz_restart(ts, now);
+}
+
+static void tick_nohz_full_update_tick(struct tick_sched *ts)
 {
 #ifdef CONFIG_NO_HZ_FULL
 	int cpu = smp_processor_id();
 
-	if (!tick_nohz_full_cpu(cpu) || is_idle_task(current))
+	if (!tick_nohz_full_cpu(cpu))
 		return;
 
 	if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
 		return;
 
-	if (!can_stop_full_tick())
-		return;
-
-	tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
+	if (can_stop_full_tick())
+		tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
+	else if (ts->tick_stopped)
+		tick_nohz_restart_sched_tick(ts, ktime_get());
 #endif
 }
 
@@ -849,7 +848,7 @@ void tick_nohz_irq_exit(void)
 	if (ts->inidle)
 		__tick_nohz_idle_enter(ts);
 	else
-		tick_nohz_full_stop_tick(ts);
+		tick_nohz_full_update_tick(ts);
 }
 
 /**
@@ -864,23 +863,6 @@ ktime_t tick_nohz_get_sleep_length(void)
 	return ts->sleep_length;
 }
 
-static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
-{
-	/* Update jiffies first */
-	tick_do_update_jiffies64(now);
-	update_cpu_load_nohz();
-
-	calc_load_exit_idle();
-	touch_softlockup_watchdog();
-	/*
-	 * Cancel the scheduled timer and restore the tick
-	 */
-	ts->tick_stopped  = 0;
-	ts->idle_exittime = now;
-
-	tick_nohz_restart(ts, now);
-}
-
 static void tick_nohz_account_idle_ticks(struct tick_sched *ts)
 {
 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
diff --git a/kernel/time/time.c b/kernel/time/time.c
index 85d5bb1d67eb..ad1bf23e6eb7 100644
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -268,10 +268,14 @@ EXPORT_SYMBOL(jiffies_to_msecs);
 
 unsigned int jiffies_to_usecs(const unsigned long j)
 {
-#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
+	/*
+	 * Hz usually doesn't go much further MSEC_PER_SEC.
+	 * jiffies_to_usecs() and usecs_to_jiffies() depend on that.
+	 */
+	BUILD_BUG_ON(HZ > USEC_PER_SEC);
+
+#if !(USEC_PER_SEC % HZ)
 	return (USEC_PER_SEC / HZ) * j;
-#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
-	return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
 #else
 # if BITS_PER_LONG == 32
 	return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;
--
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