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From: Frederic Weisbecker <fweisbec@gmail.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Rik van Riel <riel@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Alexander Graf <agraf@suse.de>,
	Luiz Capitulino <lcapitulino@redhat.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
	Andy Lutomirski <luto@amacapital.net>,
	Will deacon <will.deacon@arm.com>,
	Frederic Weisbecker <fweisbec@gmail.com>
Subject: [PATCH 3/7] context_tracking: Generalize context tracking APIs to support user and guest
Date: Tue, 10 Mar 2015 15:37:14 +0100	[thread overview]
Message-ID: <1425998238-4954-4-git-send-email-fweisbec@gmail.com> (raw)
In-Reply-To: <1425998238-4954-1-git-send-email-fweisbec@gmail.com>

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

Generalize the context tracking APIs to support various nature of
contexts. This is performed by splitting out the mechanism from
context_tracking_user_enter and context_tracking_user_exit into
context_tracking_enter and context_tracking_exit.

The nature of the context we track is now detailed in a ctx_state
parameter pushed to these APIs, allowing the same functions to not just
track kernel <> user space switching, but also kernel <> guest transitions.

But leave the old functions in order to avoid breaking ARM, which calls
these functions from assembler code, and cannot easily use C enum
parameters.

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Will deacon <will.deacon@arm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
 include/linux/context_tracking.h |  9 ++++++---
 kernel/context_tracking.c        | 43 ++++++++++++++++++++++++++--------------
 2 files changed, 34 insertions(+), 18 deletions(-)

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 427b056..7f1810a 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(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,
@@ -35,7 +37,8 @@ static inline enum ctx_state exception_enter(void)
 		return 0;
 
 	prev_ctx = this_cpu_read(context_tracking.state);
-	context_tracking_user_exit();
+	if (prev_ctx != CONTEXT_KERNEL)
+		context_tracking_exit(prev_ctx);
 
 	return prev_ctx;
 }
@@ -43,8 +46,8 @@ 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 == CONTEXT_USER)
-			context_tracking_user_enter();
+		if (prev_ctx != CONTEXT_KERNEL)
+			context_tracking_enter(prev_ctx);
 	}
 }
 
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 8ad53c9..17715d8 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(enum ctx_state state)
 {
 	unsigned long flags;
 
@@ -75,7 +75,7 @@ void context_tracking_user_enter(void)
 	WARN_ON_ONCE(!current->mm);
 
 	local_irq_save(flags);
-	if ( __this_cpu_read(context_tracking.state) != CONTEXT_USER) {
+	if ( __this_cpu_read(context_tracking.state) != state) {
 		if (__this_cpu_read(context_tracking.active)) {
 			trace_user_enter(0);
 			/*
@@ -101,24 +101,31 @@ void context_tracking_user_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, CONTEXT_USER);
+		__this_cpu_write(context_tracking.state, state);
 	}
 	local_irq_restore(flags);
 }
+NOKPROBE_SYMBOL(context_tracking_enter);
+
+void context_tracking_user_enter(void)
+{
+	context_tracking_enter(CONTEXT_USER);
+}
 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(enum ctx_state state)
 {
 	unsigned long flags;
 
@@ -129,7 +136,7 @@ void context_tracking_user_exit(void)
 		return;
 
 	local_irq_save(flags);
-	if (__this_cpu_read(context_tracking.state) == CONTEXT_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
@@ -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(CONTEXT_USER);
+}
 NOKPROBE_SYMBOL(context_tracking_user_exit);
 
 /**
-- 
2.1.4


  parent reply	other threads:[~2015-03-10 14:37 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-10 14:37 [GIT PULL] nohz: Enable full dynticks on guest mode Frederic Weisbecker
2015-03-10 14:37 ` [PATCH 1/7] ppc: Remove unused cpp symbols in kvm headers Frederic Weisbecker
2015-03-10 14:37 ` [PATCH 2/7] context_tracking: Rename context symbols to prepare for transition state Frederic Weisbecker
2015-03-10 14:37 ` Frederic Weisbecker [this message]
2015-03-10 14:37 ` [PATCH 4/7] context_tracking: Add stub context_tracking_is_enabled Frederic Weisbecker
2015-03-10 14:37 ` [PATCH 5/7] context_tracking: Run vtime_user_enter/exit only when state == CONTEXT_USER Frederic Weisbecker
2015-03-10 14:37 ` [PATCH 6/7] context_tracking: Export context_tracking_user_enter/exit Frederic Weisbecker
2015-03-10 14:37 ` [PATCH 7/7] kvm,rcu,nohz: use RCU extended quiescent state when running KVM guest Frederic Weisbecker
2015-03-16 13:48 ` [GIT PULL] nohz: Enable full dynticks on guest mode Frederic Weisbecker
2015-03-16 14:53 ` Ingo Molnar
  -- strict thread matches above, loose matches on Subject: below --
2015-03-05  2:14 [PATCH 0/7] nohz/rcu: Consider guest context as extended quiescent state (ie: enable full nohz on guest) Frederic Weisbecker
2015-03-05  2:14 ` [PATCH 3/7] context_tracking: Generalize context tracking APIs to support user and guest Frederic Weisbecker

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