Messages in this thread Patch in this message | | | From | Frederic Weisbecker <> | Subject | [PATCH 07/23] context_tracking: Ground setup for static key use | Date | Thu, 1 Aug 2013 02:31:24 +0200 |
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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> --- 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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