Commit-ID: 73d424f9af7b571276e6284617cb59726d47bf12
Gitweb: http://git.kernel.org/tip/73d424f9af7b571276e6284617cb59726d47bf12
Author: Frederic Weisbecker <fweisbec@xxxxxxxxx>
AuthorDate: Thu, 11 Jul 2013 19:42:13 +0200
Committer: Frederic Weisbecker <fweisbec@xxxxxxxxx>
CommitDate: Wed, 14 Aug 2013 17:14:47 +0200
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: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Li Zhong <zhong@xxxxxxxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Kevin Hilman <khilman@xxxxxxxxxx>
---
include/linux/context_tracking.h | 11 +++++++++--
kernel/context_tracking.c | 6 +++---
2 files changed, 12 insertions(+), 5 deletions(-)
diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 8854ead..e070ea5 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -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)
{
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index b6a186c..c178226 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -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
*
@@ -178,8 +178,8 @@ 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,
- struct task_struct *next)
+void __context_tracking_task_switch(struct task_struct *prev,
+ struct task_struct *next)
{
clear_tsk_thread_flag(prev, TIF_NOHZ);
set_tsk_thread_flag(next, TIF_NOHZ);
--
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