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Commit 73d424f9 authored by Frederic Weisbecker's avatar Frederic Weisbecker
Browse files

context_tracking: Optimize context switch off case with static keys 



No need for syscall slowpath if no CPU is full dynticks,
rather nop this in this case.

Signed-off-by: default avatarFrederic 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>
parent 48d6a816

include/linux/context_tracking.h

+9 −2
Original line number Diff line number Diff line
@@ -40,6 +40,8 @@ extern void context_tracking_cpu_set(int cpu); 


extern void context_tracking_user_enter(void);

extern void context_tracking_user_exit(void);

extern void __context_tracking_task_switch(struct task_struct *prev,

					   struct task_struct *next);



static inline void user_enter(void)

{
@@ -74,8 +76,12 @@ static inline void exception_exit(enum ctx_state prev_ctx) 
	}

}



extern void context_tracking_task_switch(struct task_struct *prev,

					 struct task_struct *next);

static inline void context_tracking_task_switch(struct task_struct *prev,

						struct task_struct *next)

{

	if (static_key_false(&context_tracking_enabled))

		__context_tracking_task_switch(prev, next);

}

#else

static inline bool context_tracking_in_user(void) { return false; }

static inline void user_enter(void) { }
@@ -112,6 +118,7 @@ static inline void guest_exit(void) 
	else

		current->flags &= ~PF_VCPU;

}



#else

static inline void guest_enter(void)

{

kernel/context_tracking.c

+3 −3
Original line number Diff line number Diff line
@@ -166,7 +166,7 @@ void context_tracking_user_exit(void) 
}



/**

 * context_tracking_task_switch - context switch the syscall callbacks

 * __context_tracking_task_switch - context switch the syscall callbacks

 * @prev: the task that is being switched out

 * @next: the task that is being switched in

 *
@@ -178,7 +178,7 @@ void context_tracking_user_exit(void) 
 * migrate to some CPU that doesn't do the context tracking. As such the TIF

 * flag may not be desired there.

 */

void context_tracking_task_switch(struct task_struct *prev,

void __context_tracking_task_switch(struct task_struct *prev,

				    struct task_struct *next)

{

	clear_tsk_thread_flag(prev, TIF_NOHZ);