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Commit 3451d024 authored by Frederic Weisbecker's avatar Frederic Weisbecker
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nohz: Rename CONFIG_NO_HZ to CONFIG_NO_HZ_COMMON 



We are planning to convert the dynticks Kconfig options layout
into a choice menu. The user must be able to easily pick
any of the following implementations: constant periodic tick,
idle dynticks, full dynticks.

As this implies a mutual exclusion, the two dynticks implementions
need to converge on the selection of a common Kconfig option in order
to ease the sharing of a common infrastructure.

It would thus seem pretty natural to reuse CONFIG_NO_HZ to
that end. It already implements all the idle dynticks code
and the full dynticks depends on all that code for now.
So ideally the choice menu would propose CONFIG_NO_HZ_IDLE and
CONFIG_NO_HZ_EXTENDED then both would select CONFIG_NO_HZ.

On the other hand we want to stay backward compatible: if
CONFIG_NO_HZ is set in an older config file, we want to
enable CONFIG_NO_HZ_IDLE by default.

But we can't afford both at the same time or we run into
a circular dependency:

1) CONFIG_NO_HZ_IDLE and CONFIG_NO_HZ_EXTENDED both select
   CONFIG_NO_HZ
2) If CONFIG_NO_HZ is set, we default to CONFIG_NO_HZ_IDLE

We might be able to support that from Kconfig/Kbuild but it
may not be wise to introduce such a confusing behaviour.

So to solve this, create a new CONFIG_NO_HZ_COMMON option
which gathers the common code between idle and full dynticks
(that common code for now is simply the idle dynticks code)
and select it from their referring Kconfig.

Then we'll later create CONFIG_NO_HZ_IDLE and map CONFIG_NO_HZ
to it for backward compatibility.

Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
parent ab71d36d

Documentation/RCU/stallwarn.txt

+1 −1
Original line number Diff line number Diff line
@@ -176,7 +176,7 @@ o A CPU-bound real-time task in a CONFIG_PREEMPT_RT kernel that 
o	A hardware or software issue shuts off the scheduler-clock

	interrupt on a CPU that is not in dyntick-idle mode.  This

	problem really has happened, and seems to be most likely to

	result in RCU CPU stall warnings for CONFIG_NO_HZ=n kernels.

	result in RCU CPU stall warnings for CONFIG_NO_HZ_COMMON=n kernels.



o	A bug in the RCU implementation.

Documentation/cpu-freq/governors.txt

+2 −2
Original line number Diff line number Diff line
@@ -131,8 +131,8 @@ sampling_rate_min: 
The sampling rate is limited by the HW transition latency:

transition_latency * 100

Or by kernel restrictions:

If CONFIG_NO_HZ is set, the limit is 10ms fixed.

If CONFIG_NO_HZ is not set or nohz=off boot parameter is used, the

If CONFIG_NO_HZ_COMMON is set, the limit is 10ms fixed.

If CONFIG_NO_HZ_COMMON is not set or nohz=off boot parameter is used, the

limits depend on the CONFIG_HZ option:

HZ=1000: min=20000us  (20ms)

HZ=250:  min=80000us  (80ms)

arch/um/include/shared/common-offsets.h

+2 −2
Original line number Diff line number Diff line
@@ -30,8 +30,8 @@ DEFINE(UM_NSEC_PER_USEC, NSEC_PER_USEC); 
#ifdef CONFIG_PRINTK

DEFINE(UML_CONFIG_PRINTK, CONFIG_PRINTK);

#endif

#ifdef CONFIG_NO_HZ

DEFINE(UML_CONFIG_NO_HZ, CONFIG_NO_HZ);

#ifdef CONFIG_NO_HZ_COMMON

DEFINE(UML_CONFIG_NO_HZ_COMMON, CONFIG_NO_HZ_COMMON);

#endif

#ifdef CONFIG_UML_X86

DEFINE(UML_CONFIG_UML_X86, CONFIG_UML_X86);

arch/um/os-Linux/time.c

+1 −1
Original line number Diff line number Diff line
@@ -79,7 +79,7 @@ long long os_nsecs(void) 
	return timeval_to_ns(&tv);

}



#ifdef UML_CONFIG_NO_HZ

#ifdef UML_CONFIG_NO_HZ_COMMON

static int after_sleep_interval(struct timespec *ts)

{

	return 0;

include/linux/sched.h

+4 −4
Original line number Diff line number Diff line
@@ -230,7 +230,7 @@ extern void init_idle_bootup_task(struct task_struct *idle); 


extern int runqueue_is_locked(int cpu);



#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ)

#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)

extern void nohz_balance_enter_idle(int cpu);

extern void set_cpu_sd_state_idle(void);

extern int get_nohz_timer_target(void);
@@ -1758,13 +1758,13 @@ static inline int set_cpus_allowed_ptr(struct task_struct *p, 
}

#endif



#ifdef CONFIG_NO_HZ

#ifdef CONFIG_NO_HZ_COMMON

void calc_load_enter_idle(void);

void calc_load_exit_idle(void);

#else

static inline void calc_load_enter_idle(void) { }

static inline void calc_load_exit_idle(void) { }

#endif /* CONFIG_NO_HZ */

#endif /* CONFIG_NO_HZ_COMMON */



#ifndef CONFIG_CPUMASK_OFFSTACK

static inline int set_cpus_allowed(struct task_struct *p, cpumask_t new_mask)
@@ -1850,7 +1850,7 @@ extern void idle_task_exit(void); 
static inline void idle_task_exit(void) {}

#endif



#if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)

#if defined(CONFIG_NO_HZ_COMMON) && defined(CONFIG_SMP)

extern void wake_up_nohz_cpu(int cpu);

#else

static inline void wake_up_nohz_cpu(int cpu) { }