nohz: Separate out irq exit and idle loop dyntick logic

The tick_nohz_stop_sched_tick() function, which tries to delay
the next timer tick as long as possible, can be called from two
places:

- From the idle loop to start the dytick idle mode
- From interrupt exit if we have interrupted the dyntick
idle mode, so that we reprogram the next tick event in
case the irq changed some internal state that requires this
action.

There are only few minor differences between both that
are handled by that function, driven by the ts->inidle
cpu variable and the inidle parameter. The whole guarantees
that we only update the dyntick mode on irq exit if we actually
interrupted the dyntick idle mode, and that we enter in RCU extended
quiescent state from idle loop entry only.

Split this function into:

- tick_nohz_idle_enter(), which sets ts->inidle to 1, enters
dynticks idle mode unconditionally if it can, and enters into RCU
extended quiescent state.

- tick_nohz_irq_exit() which only updates the dynticks idle mode
when ts->inidle is set (ie: if tick_nohz_idle_enter() has been called).

To maintain symmetry, tick_nohz_restart_sched_tick() has been renamed
into tick_nohz_idle_exit().

This simplifies the code and micro-optimize the irq exit path (no need
for local_irq_save there). This also prepares for the split between
dynticks and rcu extended quiescent state logics. We'll need this split to
further fix illegal uses of RCU in extended quiescent states in the idle
loop.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: David Miller <davem@davemloft.net>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

16 files changed, 34 insertions, 34 deletions

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 3d0c6fb74ae4..3f1f8daf703c 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -183,7 +183,7 @@ void cpu_idle(void)
 
         /* endless idle loop with no priority at all */
         while (1) {
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
                 leds_event(led_idle_start);
                 while (!need_resched()) {
 #ifdef CONFIG_HOTPLUG_CPU
@@ -213,7 +213,7 @@ void cpu_idle(void)
                         }
                 }
                 leds_event(led_idle_end);
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
                 preempt_enable_no_resched();
                 schedule();
                 preempt_disable();
diff --git a/arch/avr32/kernel/process.c b/arch/avr32/kernel/process.c
index ef5a2a08fcca..6ee7952248db 100644
--- a/arch/avr32/kernel/process.c
+++ b/arch/avr32/kernel/process.c
@@ -34,10 +34,10 @@ void cpu_idle(void)
 {
         /* endless idle loop with no priority at all */
         while (1) {
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
                 while (!need_resched())
                         cpu_idle_sleep();
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
                 preempt_enable_no_resched();
                 schedule();
                 preempt_disable();
diff --git a/arch/blackfin/kernel/process.c b/arch/blackfin/kernel/process.c
index 6a80a9e9fc4a..7b141b5c9e8d 100644
--- a/arch/blackfin/kernel/process.c
+++ b/arch/blackfin/kernel/process.c
@@ -88,10 +88,10 @@ void cpu_idle(void)
 #endif
                 if (!idle)
                         idle = default_idle;
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
                 while (!need_resched())
                         idle();
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
                 preempt_enable_no_resched();
                 schedule();
                 preempt_disable();
diff --git a/arch/microblaze/kernel/process.c b/arch/microblaze/kernel/process.c
index 95cc295976a7..5407f09b4be4 100644
--- a/arch/microblaze/kernel/process.c
+++ b/arch/microblaze/kernel/process.c
@@ -103,10 +103,10 @@ void cpu_idle(void)
                 if (!idle)
                         idle = default_idle;
 
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
                 while (!need_resched())
                         idle();
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
 
                 preempt_enable_no_resched();
                 schedule();
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index c47f96e453c0..c11e5ca2a434 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -56,7 +56,7 @@ void __noreturn cpu_idle(void)
 
         /* endless idle loop with no priority at all */
         while (1) {
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
                 while (!need_resched() && cpu_online(cpu)) {
 #ifdef CONFIG_MIPS_MT_SMTC
                         extern void smtc_idle_loop_hook(void);
@@ -77,7 +77,7 @@ void __noreturn cpu_idle(void)
                      system_state == SYSTEM_BOOTING))
                         play_dead();
 #endif
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
                 preempt_enable_no_resched();
                 schedule();
                 preempt_disable();
diff --git a/arch/openrisc/kernel/idle.c b/arch/openrisc/kernel/idle.c
index d5bc5f813e89..fb6a9bf40006 100644
--- a/arch/openrisc/kernel/idle.c
+++ b/arch/openrisc/kernel/idle.c
@@ -51,7 +51,7 @@ void cpu_idle(void)
 
         /* endless idle loop with no priority at all */
         while (1) {
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
 
                 while (!need_resched()) {
                         check_pgt_cache();
@@ -69,7 +69,7 @@ void cpu_idle(void)
                         set_thread_flag(TIF_POLLING_NRFLAG);
                 }
 
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
                 preempt_enable_no_resched();
                 schedule();
                 preempt_disable();
diff --git a/arch/powerpc/kernel/idle.c b/arch/powerpc/kernel/idle.c
index 39a2baa6ad58..878572f70ac5 100644
--- a/arch/powerpc/kernel/idle.c
+++ b/arch/powerpc/kernel/idle.c
@@ -56,7 +56,7 @@ void cpu_idle(void)
 
         set_thread_flag(TIF_POLLING_NRFLAG);
         while (1) {
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
                 while (!need_resched() && !cpu_should_die()) {
                         ppc64_runlatch_off();
 
@@ -93,7 +93,7 @@ void cpu_idle(void)
 
                 HMT_medium();
                 ppc64_runlatch_on();
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
                 preempt_enable_no_resched();
                 if (cpu_should_die())
                         cpu_die();
diff --git a/arch/powerpc/platforms/iseries/setup.c b/arch/powerpc/platforms/iseries/setup.c
index ea0acbd8966d..e83dfaf89f69 100644
--- a/arch/powerpc/platforms/iseries/setup.c
+++ b/arch/powerpc/platforms/iseries/setup.c
@@ -563,7 +563,7 @@ static void yield_shared_processor(void)
 static void iseries_shared_idle(void)
 {
         while (1) {
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
                 while (!need_resched() && !hvlpevent_is_pending()) {
                         local_irq_disable();
                         ppc64_runlatch_off();
@@ -577,7 +577,7 @@ static void iseries_shared_idle(void)
                 }
 
                 ppc64_runlatch_on();
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
 
                 if (hvlpevent_is_pending())
                         process_iSeries_events();
@@ -593,7 +593,7 @@ static void iseries_dedicated_idle(void)
         set_thread_flag(TIF_POLLING_NRFLAG);
 
         while (1) {
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
                 if (!need_resched()) {
                         while (!need_resched()) {
                                 ppc64_runlatch_off();
@@ -610,7 +610,7 @@ static void iseries_dedicated_idle(void)
                 }
 
                 ppc64_runlatch_on();
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
                 preempt_enable_no_resched();
                 schedule();
                 preempt_disable();
diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index 9451b210a1b4..6224f9dbbc1f 100644
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -91,10 +91,10 @@ static void default_idle(void)
 void cpu_idle(void)
 {
         for (;;) {
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
                 while (!need_resched())
                         default_idle();
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
                 preempt_enable_no_resched();
                 schedule();
                 preempt_disable();
diff --git a/arch/sh/kernel/idle.c b/arch/sh/kernel/idle.c
index db4ecd731a00..6015743020a0 100644
--- a/arch/sh/kernel/idle.c
+++ b/arch/sh/kernel/idle.c
@@ -89,7 +89,7 @@ void cpu_idle(void)
 
         /* endless idle loop with no priority at all */
         while (1) {
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
 
                 while (!need_resched()) {
                         check_pgt_cache();
@@ -111,7 +111,7 @@ void cpu_idle(void)
                         start_critical_timings();
                 }
 
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
                 preempt_enable_no_resched();
                 schedule();
                 preempt_disable();
diff --git a/arch/sparc/kernel/process_64.c b/arch/sparc/kernel/process_64.c
index 3739a06a76cb..9c2795ba2cfe 100644
--- a/arch/sparc/kernel/process_64.c
+++ b/arch/sparc/kernel/process_64.c
@@ -95,12 +95,12 @@ void cpu_idle(void)
         set_thread_flag(TIF_POLLING_NRFLAG);
 
         while(1) {
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
 
                 while (!need_resched() && !cpu_is_offline(cpu))
                         sparc64_yield(cpu);
 
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
 
                 preempt_enable_no_resched();
 
diff --git a/arch/tile/kernel/process.c b/arch/tile/kernel/process.c
index 9c45d8bbdf57..920e674aedb9 100644
--- a/arch/tile/kernel/process.c
+++ b/arch/tile/kernel/process.c
@@ -85,7 +85,7 @@ void cpu_idle(void)
 
         /* endless idle loop with no priority at all */
         while (1) {
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
                 while (!need_resched()) {
                         if (cpu_is_offline(cpu))
                                 BUG();  /* no HOTPLUG_CPU */
@@ -105,7 +105,7 @@ void cpu_idle(void)
                                 local_irq_enable();
                         current_thread_info()->status |= TS_POLLING;
                 }
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
                 preempt_enable_no_resched();
                 schedule();
                 preempt_disable();
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index c5338351aecd..cfb657e92849 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -246,10 +246,10 @@ void default_idle(void)
                 if (need_resched())
                         schedule();
 
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
                 nsecs = disable_timer();
                 idle_sleep(nsecs);
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
         }
 }
 
diff --git a/arch/unicore32/kernel/process.c b/arch/unicore32/kernel/process.c
index ba401df971ed..9999b9a84d46 100644
--- a/arch/unicore32/kernel/process.c
+++ b/arch/unicore32/kernel/process.c
@@ -55,7 +55,7 @@ void cpu_idle(void)
 {
         /* endless idle loop with no priority at all */
         while (1) {
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
                 while (!need_resched()) {
                         local_irq_disable();
                         stop_critical_timings();
@@ -63,7 +63,7 @@ void cpu_idle(void)
                         local_irq_enable();
                         start_critical_timings();
                 }
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
                 preempt_enable_no_resched();
                 schedule();
                 preempt_disable();
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 795b79f984c2..6d9d4d52cac5 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -99,7 +99,7 @@ void cpu_idle(void)
 
         /* endless idle loop with no priority at all */
         while (1) {
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
                 while (!need_resched()) {
 
                         check_pgt_cache();
@@ -116,7 +116,7 @@ void cpu_idle(void)
                                 pm_idle();
                         start_critical_timings();
                 }
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
                 preempt_enable_no_resched();
                 schedule();
                 preempt_disable();
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 3bd7e6eebf31..b069e9d7875f 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -122,7 +122,7 @@ void cpu_idle(void)
 
         /* endless idle loop with no priority at all */
         while (1) {
-                tick_nohz_stop_sched_tick(1);
+                tick_nohz_idle_enter();
                 while (!need_resched()) {
 
                         rmb();
@@ -149,7 +149,7 @@ void cpu_idle(void)
                         __exit_idle();
                 }
 
-                tick_nohz_restart_sched_tick();
+                tick_nohz_idle_exit();
                 preempt_enable_no_resched();
                 schedule();
                 preempt_disable();