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context_tracking: Ground setup for static key use 

Prepare for using a static key in the context tracking subsystem.
This will help optimizing the off case on its many users:

* user_enter, user_exit, exception_enter, exception_exit, guest_enter,
  guest_exit, vtime_*()

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Kevin Hilman <khilman@linaro.org>
This commit is contained in:
Frederic Weisbecker 2013-07-11 19:12:32 +02:00
parent d84d27a491
commit 65f382fd0c
3 changed files with 29 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
include/linux/context_tracking.h
View File

@ -4,6 +4,7 @@
#include <linux/sched.h>
#include <linux/percpu.h>
#include <linux/vtime.h>
#include <linux/static_key.h>
#include <asm/ptrace.h>
struct context_tracking {
@ -22,6 +23,7 @@ struct context_tracking {
#ifdef CONFIG_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)
@ -67,6 +69,14 @@ static inline void context_tracking_task_switch(struct task_struct *prev,
struct task_struct *next) { }
#endif /* !CONFIG_CONTEXT_TRACKING */
#ifdef CONFIG_CONTEXT_TRACKING_FORCE
extern void context_tracking_init(void);
#else
static inline void context_tracking_init(void) { }
#endif /* CONFIG_CONTEXT_TRACKING_FORCE */
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
extern void guest_enter(void);
extern void guest_exit(void);

2
init/main.c
View File

@ -75,6 +75,7 @@
#include <linux/blkdev.h>
#include <linux/elevator.h>
#include <linux/sched_clock.h>
#include <linux/context_tracking.h>
#include <asm/io.h>
#include <asm/bugs.h>
@ -545,6 +546,7 @@ asmlinkage void __init start_kernel(void)
idr_init_cache();
rcu_init();
tick_nohz_init();
context_tracking_init();
radix_tree_init();
/* init some links before init_ISA_irqs() */
early_irq_init();

23
kernel/context_tracking.c
View File

@ -20,15 +20,16 @@
#include <linux/hardirq.h>
#include <linux/export.h>
DEFINE_PER_CPU(struct context_tracking, context_tracking) = {
#ifdef CONFIG_CONTEXT_TRACKING_FORCE
.active = true,
#endif
};
struct static_key context_tracking_enabled = STATIC_KEY_INIT_FALSE;
DEFINE_PER_CPU(struct context_tracking, context_tracking);
void context_tracking_cpu_set(int cpu)
{
per_cpu(context_tracking.active, cpu) = true;
if (!per_cpu(context_tracking.active, cpu)) {
per_cpu(context_tracking.active, cpu) = true;
static_key_slow_inc(&context_tracking_enabled);
}
}
/**
@ -202,3 +203,13 @@ void context_tracking_task_switch(struct task_struct *prev,
clear_tsk_thread_flag(prev, TIF_NOHZ);
set_tsk_thread_flag(next, TIF_NOHZ);
}
#ifdef CONFIG_CONTEXT_TRACKING_FORCE
void __init context_tracking_init(void)
{
int cpu;
for_each_possible_cpu(cpu)
context_tracking_cpu_set(cpu);
}
#endif