[PATCH] context_tracking: remove duplicate enabled check

[PATCH] context_tracking: remove duplicate enabled check

[Paolo Bonzini]

All calls to context_tracking_enter and context_tracking_exit
are already checking context_tracking_is_enabled, except the
context_tracking_user_enter and context_tracking_user_exit
functions left in for the benefit of assembly calls.

Pull the check up to those functions, by making them simple
wrappers around the user_enter and user_exit inline functions.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/linux/context_tracking.h |  4 ++--
 kernel/context_tracking.c        | 16 ++--------------
 2 files changed, 4 insertions(+), 16 deletions(-)

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 2821838256b4..a20a2badbc5f 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -20,13 +20,13 @@ extern void __context_tracking_task_switch(struct task_struct *prev,
 static inline void user_enter(void)
 {
 	if (context_tracking_is_enabled())
-		context_tracking_user_enter();
+		context_tracking_enter(CONTEXT_USER);
 
 }
 static inline void user_exit(void)
 {
 	if (context_tracking_is_enabled())
-		context_tracking_user_exit();
+		context_tracking_exit(CONTEXT_USER);
 }
 
 static inline enum ctx_state exception_enter(void)
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 72d59a1a6eb6..ccdc188884d7 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -52,15 +52,6 @@ void context_tracking_enter(enum ctx_state state)
 	unsigned long flags;
 
 	/*
-	 * Repeat the user_enter() check here because some archs may be calling
-	 * this from asm and if no CPU needs context tracking, they shouldn't
-	 * go further. Repeat the check here until they support the inline static
-	 * key check.
-	 */
-	if (!context_tracking_is_enabled())
-		return;
-
-	/*
 	 * Some contexts may involve an exception occuring in an irq,
 	 * leading to that nesting:
 	 * rcu_irq_enter() rcu_user_exit() rcu_user_exit() rcu_irq_exit()
@@ -112,7 +103,7 @@ EXPORT_SYMBOL_GPL(context_tracking_enter);
 
 void context_tracking_user_enter(void)
 {
-	context_tracking_enter(CONTEXT_USER);
+	user_enter();
 }
 NOKPROBE_SYMBOL(context_tracking_user_enter);
 
@@ -132,9 +123,6 @@ void context_tracking_exit(enum ctx_state state)
 {
 	unsigned long flags;
 
-	if (!context_tracking_is_enabled())
-		return;
-
 	if (in_interrupt())
 		return;
 
@@ -160,7 +148,7 @@ EXPORT_SYMBOL_GPL(context_tracking_exit);
 
 void context_tracking_user_exit(void)
 {
-	context_tracking_exit(CONTEXT_USER);
+	user_exit();
 }
 NOKPROBE_SYMBOL(context_tracking_user_exit);
 
-- 
2.3.5

Re: [PATCH] context_tracking: remove duplicate enabled check

[Rik van Riel]

On 04/28/2015 07:36 AM, Paolo Bonzini wrote:
> All calls to context_tracking_enter and context_tracking_exit
> are already checking context_tracking_is_enabled, except the
> context_tracking_user_enter and context_tracking_user_exit
> functions left in for the benefit of assembly calls.
> 
> Pull the check up to those functions, by making them simple
> wrappers around the user_enter and user_exit inline functions.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Reviewed-by: Rik van Riel <riel@redhat.com>

-- 
All rights reversed

Re: [PATCH] context_tracking: remove duplicate enabled check

[Rik van Riel]

On 04/28/2015 07:36 AM, Paolo Bonzini wrote:
> All calls to context_tracking_enter and context_tracking_exit
> are already checking context_tracking_is_enabled, except the
> context_tracking_user_enter and context_tracking_user_exit
> functions left in for the benefit of assembly calls.
> 
> Pull the check up to those functions, by making them simple
> wrappers around the user_enter and user_exit inline functions.

With this and your other (not yet posted) patch, run time
for the kvm-unit-tests vmexit.flat vmcall test with 10
million iterations drops from 17.8 to 17.5 seconds, which
is about a 1.7% speedup.


-- 
All rights reversed