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 <fweis...@gmail.com>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Li Zhong <zh...@linux.vnet.ibm.com>
Cc: Mike Galbraith <efa...@gmx.de>
Cc: Kevin Hilman <khil...@linaro.org>
---
include/linux/context_tracking.h | 2 ++
kernel/context_tracking.c | 26 ++++++++++++++++++++------
2 files changed, 22 insertions(+), 6 deletions(-)
diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 1ae37c7..f9356eb 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -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)
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 72bcb25..f07505c 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -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 +203,16 @@ 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
+static int __init context_tracking_init(void)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu)
+ context_tracking_cpu_set(cpu);
+
+ return 0;
+}
+early_initcall(context_tracking_init);
+#endif
--
1.7.5.4
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