[GIT PULL] NOHZ updates for v4.3

From: Ingo Molnar
Date: Mon Aug 31 2015 - 13:29:17 EST

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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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Next message: Sylvain Rochet: "Re: [PATCH] regmap: fix NULL pointer dereference in __regmap_init if bus is NULL"
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