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>
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 72bcb25..839d377 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 +203,13 @@
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