linux-kernel - [PATCH 1/6] rcu,nohz: add context_tracking_user

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Date:	Tue, 10 Feb 2015 09:41:45 -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 1/6] rcu,nohz: add context_tracking_user_enter/exit wrapper functions

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

These wrapper functions allow architecture code (eg. ARM) to keep
calling context_tracking_user_enter & context_tracking_user_exit
the same way it always has, without error prone tricks like duplicate
defines of argument values in assembly code.

Signed-off-by: Rik van Riel <riel@...hat.com>
---
 include/linux/context_tracking.h |  2 ++
 kernel/context_tracking.c        | 37 +++++++++++++++++++++++++------------
 2 files changed, 27 insertions(+), 12 deletions(-)

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 37b81bd51ec0..03b9c733eae7 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -10,6 +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_user_enter(void);
 extern void context_tracking_user_exit(void);
 extern void __context_tracking_task_switch(struct task_struct *prev,
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 937ecdfdf258..bbdc423936e6 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -39,15 +39,15 @@ void context_tracking_cpu_set(int cpu)
 }
 
 /**
- * context_tracking_user_enter - Inform the context tracking that the CPU is going to
- *                               enter userspace mode.
+ * context_tracking_enter - Inform the context tracking that the CPU is going
+ *                          enter user or guest space mode.
  *
  * This function must be called right before we switch from the kernel
- * to userspace, when it's guaranteed the remaining kernel instructions
- * to execute won't use any RCU read side critical section because this
- * function sets RCU in extended quiescent state.
+ * to user or guest space, when it's guaranteed the remaining kernel
+ * instructions to execute won't use any RCU read side critical section
+ * because this function sets RCU in extended quiescent state.
  */
-void context_tracking_user_enter(void)
+void context_tracking_enter(void)
 {
 	unsigned long flags;
 
@@ -105,20 +105,27 @@ void context_tracking_user_enter(void)
 	}
 	local_irq_restore(flags);
 }
+NOKPROBE_SYMBOL(context_tracking_enter);
+
+void context_tracking_user_enter(void)
+{
+	context_tracking_enter();
+}
 NOKPROBE_SYMBOL(context_tracking_user_enter);
 
 /**
- * context_tracking_user_exit - Inform the context tracking that the CPU is
- *                              exiting userspace mode and entering the kernel.
+ * context_tracking_exit - Inform the context tracking that the CPU is
+ *                         exiting user or guest mode and entering the kernel.
  *
- * This function must be called after we entered the kernel from userspace
- * before any use of RCU read side critical section. This potentially include
- * any high level kernel code like syscalls, exceptions, signal handling, etc...
+ * This function must be called after we entered the kernel from user or
+ * guest space before any use of RCU read side critical section. This
+ * potentially include any high level kernel code like syscalls, exceptions,
+ * signal handling, etc...
  *
  * 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_user_exit(void)
+void context_tracking_exit(void)
 {
 	unsigned long flags;
 
@@ -143,6 +150,12 @@ void context_tracking_user_exit(void)
 	}
 	local_irq_restore(flags);
 }
+NOKPROBE_SYMBOL(context_tracking_exit);
+
+void context_tracking_user_exit(void)
+{
+	context_tracking_exit();
+}
 NOKPROBE_SYMBOL(context_tracking_user_exit);
 
 /**
-- 
1.9.3

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