linux-kernel - [PATCH 2/6] rcu,nohz: add state parameter to context_tracking

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Date:	Tue, 10 Feb 2015 09:41:46 -0500
From:	riel@...hat.com
To:	paulmck@...ux.vnet.ibm.com
Cc:	will.deacon@....com, linux-kernel@...r.kernel.org,
	Catalin.Marinas@....com, fweisbec@...il.com, kvm@...r.kernel.org,
	mtosatti@...hat.com, borntraeger@...ibm.com, mingo@...nel.org,
	oleg@...hat.com, lcapitulino@...hat.com, pbonzini@...hat.com
Subject: [PATCH 2/6] rcu,nohz: add state parameter to context_tracking_enter/exit

From: Rik van Riel <riel@...hat.com>

Add the expected ctx_state as a parameter to context_tracking_enter and
context_tracking_exit, allowing the same functions to not just track
kernel <> user space switching, but also kernel <> guest transitions.

Signed-off-by: Rik van Riel <riel@...hat.com>
---
 include/linux/context_tracking.h | 10 +++++-----
 kernel/context_tracking.c        | 14 +++++++-------
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 03b9c733eae7..954253283709 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -10,8 +10,8 @@
 #ifdef CONFIG_CONTEXT_TRACKING
 extern void context_tracking_cpu_set(int cpu);
 
-extern void context_tracking_enter(void);
-extern void context_tracking_exit(void);
+extern void context_tracking_enter(enum ctx_state state);
+extern void context_tracking_exit(enum ctx_state state);
 extern void context_tracking_user_enter(void);
 extern void context_tracking_user_exit(void);
 extern void __context_tracking_task_switch(struct task_struct *prev,
@@ -37,7 +37,7 @@ static inline enum ctx_state exception_enter(void)
 		return 0;
 
 	prev_ctx = this_cpu_read(context_tracking.state);
-	context_tracking_user_exit();
+	context_tracking_exit(prev_ctx);
 
 	return prev_ctx;
 }
@@ -45,8 +45,8 @@ static inline enum ctx_state exception_enter(void)
 static inline void exception_exit(enum ctx_state prev_ctx)
 {
 	if (context_tracking_is_enabled()) {
-		if (prev_ctx == IN_USER)
-			context_tracking_user_enter();
+		if (prev_ctx != IN_KERNEL)
+			context_tracking_enter(prev_ctx);
 	}
 }
 
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index bbdc423936e6..38e38aeac8b9 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -47,7 +47,7 @@ void context_tracking_cpu_set(int cpu)
  * instructions to execute won't use any RCU read side critical section
  * because this function sets RCU in extended quiescent state.
  */
-void context_tracking_enter(void)
+void context_tracking_enter(enum ctx_state state)
 {
 	unsigned long flags;
 
@@ -75,7 +75,7 @@ void context_tracking_enter(void)
 	WARN_ON_ONCE(!current->mm);
 
 	local_irq_save(flags);
-	if ( __this_cpu_read(context_tracking.state) != IN_USER) {
+	if ( __this_cpu_read(context_tracking.state) != state) {
 		if (__this_cpu_read(context_tracking.active)) {
 			trace_user_enter(0);
 			/*
@@ -101,7 +101,7 @@ void context_tracking_enter(void)
 		 * OTOH we can spare the calls to vtime and RCU when context_tracking.active
 		 * is false because we know that CPU is not tickless.
 		 */
-		__this_cpu_write(context_tracking.state, IN_USER);
+		__this_cpu_write(context_tracking.state, state);
 	}
 	local_irq_restore(flags);
 }
@@ -109,7 +109,7 @@ NOKPROBE_SYMBOL(context_tracking_enter);
 
 void context_tracking_user_enter(void)
 {
-	context_tracking_enter();
+	context_tracking_enter(IN_USER);
 }
 NOKPROBE_SYMBOL(context_tracking_user_enter);
 
@@ -125,7 +125,7 @@ NOKPROBE_SYMBOL(context_tracking_user_enter);
  * This call supports re-entrancy. This way it can be called from any exception
  * handler without needing to know if we came from userspace or not.
  */
-void context_tracking_exit(void)
+void context_tracking_exit(enum ctx_state state)
 {
 	unsigned long flags;
 
@@ -136,7 +136,7 @@ void context_tracking_exit(void)
 		return;
 
 	local_irq_save(flags);
-	if (__this_cpu_read(context_tracking.state) == IN_USER) {
+	if (__this_cpu_read(context_tracking.state) == state) {
 		if (__this_cpu_read(context_tracking.active)) {
 			/*
 			 * We are going to run code that may use RCU. Inform
@@ -154,7 +154,7 @@ NOKPROBE_SYMBOL(context_tracking_exit);
 
 void context_tracking_user_exit(void)
 {
-	context_tracking_exit();
+	context_tracking_exit(IN_USER);
 }
 NOKPROBE_SYMBOL(context_tracking_user_exit);
 
-- 
1.9.3

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