[PATCH 0/3] preempt: Fix tracing crash

[PATCH 0/3] preempt: Fix tracing crash

[Frederic Weisbecker]

This is a proposition to fix the function graph tracer crashes reported
by Fengguang Wu's 0-day testing.

git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
	sched/core

HEAD: 723d604e2c185b94c6890c26dab9c72e4243711b

Thanks,
	Frederic
---

Frederic Weisbecker (3):
      sched: Make preempt_schedule_context() function-tracing safe
      preempt: Use preempt_schedule_context() as the official tracing preemption point
      preempt: Reorganize a bit the notrace declensions


 arch/x86/include/asm/preempt.h   |  8 +++-----
 arch/x86/kernel/i386_ksyms_32.c  |  4 +---
 arch/x86/kernel/x8664_ksyms_64.c |  4 +---
 arch/x86/lib/thunk_32.S          |  4 +---
 arch/x86/lib/thunk_64.S          |  4 +---
 include/asm-generic/preempt.h    |  7 ++-----
 include/linux/preempt.h          | 36 +++++++++++++++---------------------
 kernel/sched/core.c              | 19 ++++++++++++-------
 8 files changed, 36 insertions(+), 50 deletions(-)

[PATCH 1/3] sched: Make preempt_schedule_context() function-tracing safe

[Frederic Weisbecker]

Since function tracing disables preemption, it needs a safe preemption
point to use when preemption is re-enabled without worrying about tracing
recursion. Ie: to avoid tracing recursion, that preemption point can't
be traced (use of notrace qualifier) and it can't call any traceable
function before that preemption point disables preemption itself, which
disarms the recursion.

preempt_schedule() was fine until commit
b30f0e3ffedfa52b1d67a302ae5860c49998e5e2
("sched/preempt: Optimize preemption operations on __schedule() callers")
because PREEMPT_ACTIVE (which has the property to disable preemption
and this disarm tracing preemption recursion) was set before calling
any further function.

But that commit introduced the use of preempt_count_add/sub() functions
to set PREEMPT_ACTIVE and because these functions are called before
preemption gets a chance to be disabled, we have a tracing recursion.

preempt_schedule_context() is one of the possible preemption functions
used by tracing. Its special purpose is to avoid tracing recursion
against context tracking. Lets enhance this function to become more
generally tracing safe by disabling preemption with raw accessors, such
that no function is called before preemption gets disabled and disarm
the tracing recursion.

This function is going to become the specific tracing-safe preemption
point in further commit.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
 kernel/sched/core.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5140db6..4c3d41f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2960,7 +2960,13 @@ asmlinkage __visible void __sched notrace preempt_schedule_context(void)
 		return;
 
 	do {
-		preempt_active_enter();
+		/*
+		 * Use raw __prempt_count() ops that don't call function.
+		 * We can't call functions before disabling preemption which
+		 * disarm preemption tracing recursions.
+		 */
+		__preempt_count_add(PREEMPT_ACTIVE + PREEMPT_DISABLE_OFFSET);
+		barrier();
 		/*
 		 * Needs preempt disabled in case user_exit() is traced
 		 * and the tracer calls preempt_enable_notrace() causing
@@ -2970,7 +2976,8 @@ asmlinkage __visible void __sched notrace preempt_schedule_context(void)
 		__schedule();
 		exception_exit(prev_ctx);
 
-		preempt_active_exit();
+		barrier();
+		__preempt_count_sub(PREEMPT_ACTIVE + PREEMPT_DISABLE_OFFSET);
 	} while (need_resched());
 }
 EXPORT_SYMBOL_GPL(preempt_schedule_context);
-- 
2.1.4

[PATCH 2/3] preempt: Use preempt_schedule_context() as the official tracing preemption point

[Frederic Weisbecker]

preempt_schedule_context() is a tracing safe preemption point but it's
only used when CONFIG_CONTEXT_TRACKING=y. Other configs have tracing
recursion issues since b30f0e3ffedfa52b1d67a302ae5860c49998e5e2
("sched/preempt: Optimize preemption operations on __schedule() callers")
introduced function based preemp_coun_*() ops.

Lets make it available on all configs and give it a more appropriate
name for its new position.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
 arch/x86/include/asm/preempt.h   | 8 +++-----
 arch/x86/kernel/i386_ksyms_32.c  | 4 +---
 arch/x86/kernel/x8664_ksyms_64.c | 4 +---
 arch/x86/lib/thunk_32.S          | 4 +---
 arch/x86/lib/thunk_64.S          | 4 +---
 include/asm-generic/preempt.h    | 7 ++-----
 include/linux/preempt.h          | 6 +-----
 kernel/sched/core.c              | 8 +++-----
 8 files changed, 13 insertions(+), 32 deletions(-)

diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
index 8f327184..dca7171 100644
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -99,11 +99,9 @@ static __always_inline bool should_resched(void)
   extern asmlinkage void ___preempt_schedule(void);
 # define __preempt_schedule() asm ("call ___preempt_schedule")
   extern asmlinkage void preempt_schedule(void);
-# ifdef CONFIG_CONTEXT_TRACKING
-    extern asmlinkage void ___preempt_schedule_context(void);
-#   define __preempt_schedule_context() asm ("call ___preempt_schedule_context")
-    extern asmlinkage void preempt_schedule_context(void);
-# endif
+  extern asmlinkage void ___preempt_schedule_notrace(void);
+# define __preempt_schedule_notrace() asm ("call ___preempt_schedule_notrace")
+  extern asmlinkage void preempt_schedule_notrace(void);
 #endif
 
 #endif /* __ASM_PREEMPT_H */
diff --git a/arch/x86/kernel/i386_ksyms_32.c b/arch/x86/kernel/i386_ksyms_32.c
index 05fd74f..64341aa 100644
--- a/arch/x86/kernel/i386_ksyms_32.c
+++ b/arch/x86/kernel/i386_ksyms_32.c
@@ -40,7 +40,5 @@ EXPORT_SYMBOL(empty_zero_page);
 
 #ifdef CONFIG_PREEMPT
 EXPORT_SYMBOL(___preempt_schedule);
-#ifdef CONFIG_CONTEXT_TRACKING
-EXPORT_SYMBOL(___preempt_schedule_context);
-#endif
+EXPORT_SYMBOL(___preempt_schedule_notrace);
 #endif
diff --git a/arch/x86/kernel/x8664_ksyms_64.c b/arch/x86/kernel/x8664_ksyms_64.c
index 37d8fa4..a0695be 100644
--- a/arch/x86/kernel/x8664_ksyms_64.c
+++ b/arch/x86/kernel/x8664_ksyms_64.c
@@ -75,7 +75,5 @@ EXPORT_SYMBOL(native_load_gs_index);
 
 #ifdef CONFIG_PREEMPT
 EXPORT_SYMBOL(___preempt_schedule);
-#ifdef CONFIG_CONTEXT_TRACKING
-EXPORT_SYMBOL(___preempt_schedule_context);
-#endif
+EXPORT_SYMBOL(___preempt_schedule_notrace);
 #endif
diff --git a/arch/x86/lib/thunk_32.S b/arch/x86/lib/thunk_32.S
index 5eb7150..e407941 100644
--- a/arch/x86/lib/thunk_32.S
+++ b/arch/x86/lib/thunk_32.S
@@ -38,8 +38,6 @@
 
 #ifdef CONFIG_PREEMPT
 	THUNK ___preempt_schedule, preempt_schedule
-#ifdef CONFIG_CONTEXT_TRACKING
-	THUNK ___preempt_schedule_context, preempt_schedule_context
-#endif
+	THUNK ___preempt_schedule_notrace, preempt_schedule_notrace
 #endif
 
diff --git a/arch/x86/lib/thunk_64.S b/arch/x86/lib/thunk_64.S
index f89ba4e9..2198902 100644
--- a/arch/x86/lib/thunk_64.S
+++ b/arch/x86/lib/thunk_64.S
@@ -49,9 +49,7 @@
 
 #ifdef CONFIG_PREEMPT
 	THUNK ___preempt_schedule, preempt_schedule
-#ifdef CONFIG_CONTEXT_TRACKING
-	THUNK ___preempt_schedule_context, preempt_schedule_context
-#endif
+	THUNK ___preempt_schedule_notrace, preempt_schedule_notrace
 #endif
 
 #if defined(CONFIG_TRACE_IRQFLAGS) \
diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h
index eb6f9e6..d0a7a47 100644
--- a/include/asm-generic/preempt.h
+++ b/include/asm-generic/preempt.h
@@ -79,11 +79,8 @@ static __always_inline bool should_resched(void)
 #ifdef CONFIG_PREEMPT
 extern asmlinkage void preempt_schedule(void);
 #define __preempt_schedule() preempt_schedule()
-
-#ifdef CONFIG_CONTEXT_TRACKING
-extern asmlinkage void preempt_schedule_context(void);
-#define __preempt_schedule_context() preempt_schedule_context()
-#endif
+extern asmlinkage void preempt_schedule_notrace(void);
+#define __preempt_schedule_notrace() preempt_schedule_notrace()
 #endif /* CONFIG_PREEMPT */
 
 #endif /* __ASM_PREEMPT_H */
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index a1a00e1..7686dd6 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -204,15 +204,11 @@ do { \
 
 #ifdef CONFIG_PREEMPT
 
-#ifndef CONFIG_CONTEXT_TRACKING
-#define __preempt_schedule_context() __preempt_schedule()
-#endif
-
 #define preempt_enable_notrace() \
 do { \
 	barrier(); \
 	if (unlikely(__preempt_count_dec_and_test())) \
-		__preempt_schedule_context(); \
+		__preempt_schedule_notrace(); \
 } while (0)
 #else
 #define preempt_enable_notrace() \
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4c3d41f..053947a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2937,9 +2937,8 @@ asmlinkage __visible void __sched notrace preempt_schedule(void)
 NOKPROBE_SYMBOL(preempt_schedule);
 EXPORT_SYMBOL(preempt_schedule);
 
-#ifdef CONFIG_CONTEXT_TRACKING
 /**
- * preempt_schedule_context - preempt_schedule called by tracing
+ * preempt_schedule_notrace - preempt_schedule called by tracing
  *
  * The tracing infrastructure uses preempt_enable_notrace to prevent
  * recursion and tracing preempt enabling caused by the tracing
@@ -2952,7 +2951,7 @@ EXPORT_SYMBOL(preempt_schedule);
  * instead of preempt_schedule() to exit user context if needed before
  * calling the scheduler.
  */
-asmlinkage __visible void __sched notrace preempt_schedule_context(void)
+asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
 {
 	enum ctx_state prev_ctx;
 
@@ -2980,8 +2979,7 @@ asmlinkage __visible void __sched notrace preempt_schedule_context(void)
 		__preempt_count_sub(PREEMPT_ACTIVE + PREEMPT_DISABLE_OFFSET);
 	} while (need_resched());
 }
-EXPORT_SYMBOL_GPL(preempt_schedule_context);
-#endif /* CONFIG_CONTEXT_TRACKING */
+EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
 
 #endif /* CONFIG_PREEMPT */
 
-- 
2.1.4

[PATCH 3/3] preempt: Reorganize a bit the notrace declensions

[Frederic Weisbecker]

preempt.h has two seperate "#ifdef CONFIG_PREEMPT" sections: one to
define preempt_enable() and another to define preempt_enable_notrace().

Lets gather both.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
 include/linux/preempt.h | 34 ++++++++++++++++------------------
 1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index 7686dd6..0f1534a 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -175,20 +175,34 @@ do { \
 		__preempt_schedule(); \
 } while (0)
 
+#define preempt_enable_notrace() \
+do { \
+	barrier(); \
+	if (unlikely(__preempt_count_dec_and_test())) \
+		__preempt_schedule_notrace(); \
+} while (0)
+
 #define preempt_check_resched() \
 do { \
 	if (should_resched()) \
 		__preempt_schedule(); \
 } while (0)
 
-#else
+#else /* !CONFIG_PREEMPT */
 #define preempt_enable() \
 do { \
 	barrier(); \
 	preempt_count_dec(); \
 } while (0)
+
+#define preempt_enable_notrace() \
+do { \
+	barrier(); \
+	__preempt_count_dec(); \
+} while (0)
+
 #define preempt_check_resched() do { } while (0)
-#endif
+#endif /* CONFIG_PREEMPT */
 
 #define preempt_disable_notrace() \
 do { \
@@ -202,22 +216,6 @@ do { \
 	__preempt_count_dec(); \
 } while (0)
 
-#ifdef CONFIG_PREEMPT
-
-#define preempt_enable_notrace() \
-do { \
-	barrier(); \
-	if (unlikely(__preempt_count_dec_and_test())) \
-		__preempt_schedule_notrace(); \
-} while (0)
-#else
-#define preempt_enable_notrace() \
-do { \
-	barrier(); \
-	__preempt_count_dec(); \
-} while (0)
-#endif
-
 #else /* !CONFIG_PREEMPT_COUNT */
 
 /*
-- 
2.1.4

Re: [PATCH 0/3] preempt: Fix tracing crash

[Peter Zijlstra]

On Thu, Jun 04, 2015 at 05:39:06PM +0200, Frederic Weisbecker wrote:
> This is a proposition to fix the function graph tracer crashes reported
> by Fengguang Wu's 0-day testing.
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
> 	sched/core
> 
> HEAD: 723d604e2c185b94c6890c26dab9c72e4243711b
> 
> Thanks,
> 	Frederic
> ---
> 
> Frederic Weisbecker (3):
>       sched: Make preempt_schedule_context() function-tracing safe
>       preempt: Use preempt_schedule_context() as the official tracing preemption point
>       preempt: Reorganize a bit the notrace declensions
> 

Thanks!

[tip:sched/core] sched: Make preempt_schedule_context() function-tracing safe

[tip-bot for Frederic Weisbecker]

Commit-ID:  be690035df893385ceaac2323b29be1fb7f2a67f
Gitweb:     http://git.kernel.org/tip/be690035df893385ceaac2323b29be1fb7f2a67f
Author:     Frederic Weisbecker <fweisbec@gmail.com>
AuthorDate: Thu, 4 Jun 2015 17:39:07 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Sun, 7 Jun 2015 15:57:41 +0200

sched: Make preempt_schedule_context() function-tracing safe

Since function tracing disables preemption, it needs a safe preemption
point to use when preemption is re-enabled without worrying about tracing
recursion. Ie: to avoid tracing recursion, that preemption point can't
be traced (use of notrace qualifier) and it can't call any traceable
function before that preemption point disables preemption itself, which
disarms the recursion.

preempt_schedule() was fine until commit:

  b30f0e3ffedf ("sched/preempt: Optimize preemption operations on __schedule() callers")

because PREEMPT_ACTIVE (which has the property to disable preemption
and this disarm tracing preemption recursion) was set before calling
any further function.

But that commit introduced the use of preempt_count_add/sub() functions
to set PREEMPT_ACTIVE and because these functions are called before
preemption gets a chance to be disabled, we have a tracing recursion.

preempt_schedule_context() is one of the possible preemption functions
used by tracing. Its special purpose is to avoid tracing recursion
against context tracking. Lets enhance this function to become more
generally tracing safe by disabling preemption with raw accessors, such
that no function is called before preemption gets disabled and disarm
the tracing recursion.

This function is going to become the specific tracing-safe preemption
point in further commit.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1433432349-1021-2-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/core.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 20b858f..4e925ea 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2960,7 +2960,13 @@ asmlinkage __visible void __sched notrace preempt_schedule_context(void)
 		return;
 
 	do {
-		preempt_active_enter();
+		/*
+		 * Use raw __prempt_count() ops that don't call function.
+		 * We can't call functions before disabling preemption which
+		 * disarm preemption tracing recursions.
+		 */
+		__preempt_count_add(PREEMPT_ACTIVE + PREEMPT_DISABLE_OFFSET);
+		barrier();
 		/*
 		 * Needs preempt disabled in case user_exit() is traced
 		 * and the tracer calls preempt_enable_notrace() causing
@@ -2970,7 +2976,8 @@ asmlinkage __visible void __sched notrace preempt_schedule_context(void)
 		__schedule();
 		exception_exit(prev_ctx);
 
-		preempt_active_exit();
+		barrier();
+		__preempt_count_sub(PREEMPT_ACTIVE + PREEMPT_DISABLE_OFFSET);
 	} while (need_resched());
 }
 EXPORT_SYMBOL_GPL(preempt_schedule_context);

[tip:sched/core] preempt: Use preempt_schedule_context() as the official tracing preemption point

[tip-bot for Frederic Weisbecker]

Commit-ID:  4eaca0a887eaee04fc7a3866d0f5b51b34030dfa
Gitweb:     http://git.kernel.org/tip/4eaca0a887eaee04fc7a3866d0f5b51b34030dfa
Author:     Frederic Weisbecker <fweisbec@gmail.com>
AuthorDate: Thu, 4 Jun 2015 17:39:08 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Sun, 7 Jun 2015 15:57:42 +0200

preempt: Use preempt_schedule_context() as the official tracing preemption point

preempt_schedule_context() is a tracing safe preemption point but it's
only used when CONFIG_CONTEXT_TRACKING=y. Other configs have tracing
recursion issues since commit:

  b30f0e3ffedf ("sched/preempt: Optimize preemption operations on __schedule() callers")

introduced function based preemp_count_*() ops.

Lets make it available on all configs and give it a more appropriate
name for its new position.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1433432349-1021-3-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/include/asm/preempt.h   | 8 +++-----
 arch/x86/kernel/i386_ksyms_32.c  | 4 +---
 arch/x86/kernel/x8664_ksyms_64.c | 4 +---
 arch/x86/lib/thunk_32.S          | 4 +---
 arch/x86/lib/thunk_64.S          | 4 +---
 include/asm-generic/preempt.h    | 7 ++-----
 include/linux/preempt.h          | 6 +-----
 kernel/sched/core.c              | 8 +++-----
 8 files changed, 13 insertions(+), 32 deletions(-)

diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
index 8f327184..dca7171 100644
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -99,11 +99,9 @@ static __always_inline bool should_resched(void)
   extern asmlinkage void ___preempt_schedule(void);
 # define __preempt_schedule() asm ("call ___preempt_schedule")
   extern asmlinkage void preempt_schedule(void);
-# ifdef CONFIG_CONTEXT_TRACKING
-    extern asmlinkage void ___preempt_schedule_context(void);
-#   define __preempt_schedule_context() asm ("call ___preempt_schedule_context")
-    extern asmlinkage void preempt_schedule_context(void);
-# endif
+  extern asmlinkage void ___preempt_schedule_notrace(void);
+# define __preempt_schedule_notrace() asm ("call ___preempt_schedule_notrace")
+  extern asmlinkage void preempt_schedule_notrace(void);
 #endif
 
 #endif /* __ASM_PREEMPT_H */
diff --git a/arch/x86/kernel/i386_ksyms_32.c b/arch/x86/kernel/i386_ksyms_32.c
index 05fd74f..64341aa 100644
--- a/arch/x86/kernel/i386_ksyms_32.c
+++ b/arch/x86/kernel/i386_ksyms_32.c
@@ -40,7 +40,5 @@ EXPORT_SYMBOL(empty_zero_page);
 
 #ifdef CONFIG_PREEMPT
 EXPORT_SYMBOL(___preempt_schedule);
-#ifdef CONFIG_CONTEXT_TRACKING
-EXPORT_SYMBOL(___preempt_schedule_context);
-#endif
+EXPORT_SYMBOL(___preempt_schedule_notrace);
 #endif
diff --git a/arch/x86/kernel/x8664_ksyms_64.c b/arch/x86/kernel/x8664_ksyms_64.c
index 37d8fa4..a0695be 100644
--- a/arch/x86/kernel/x8664_ksyms_64.c
+++ b/arch/x86/kernel/x8664_ksyms_64.c
@@ -75,7 +75,5 @@ EXPORT_SYMBOL(native_load_gs_index);
 
 #ifdef CONFIG_PREEMPT
 EXPORT_SYMBOL(___preempt_schedule);
-#ifdef CONFIG_CONTEXT_TRACKING
-EXPORT_SYMBOL(___preempt_schedule_context);
-#endif
+EXPORT_SYMBOL(___preempt_schedule_notrace);
 #endif
diff --git a/arch/x86/lib/thunk_32.S b/arch/x86/lib/thunk_32.S
index 5eb7150..e407941 100644
--- a/arch/x86/lib/thunk_32.S
+++ b/arch/x86/lib/thunk_32.S
@@ -38,8 +38,6 @@
 
 #ifdef CONFIG_PREEMPT
 	THUNK ___preempt_schedule, preempt_schedule
-#ifdef CONFIG_CONTEXT_TRACKING
-	THUNK ___preempt_schedule_context, preempt_schedule_context
-#endif
+	THUNK ___preempt_schedule_notrace, preempt_schedule_notrace
 #endif
 
diff --git a/arch/x86/lib/thunk_64.S b/arch/x86/lib/thunk_64.S
index f89ba4e9..2198902 100644
--- a/arch/x86/lib/thunk_64.S
+++ b/arch/x86/lib/thunk_64.S
@@ -49,9 +49,7 @@
 
 #ifdef CONFIG_PREEMPT
 	THUNK ___preempt_schedule, preempt_schedule
-#ifdef CONFIG_CONTEXT_TRACKING
-	THUNK ___preempt_schedule_context, preempt_schedule_context
-#endif
+	THUNK ___preempt_schedule_notrace, preempt_schedule_notrace
 #endif
 
 #if defined(CONFIG_TRACE_IRQFLAGS) \
diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h
index eb6f9e6..d0a7a47 100644
--- a/include/asm-generic/preempt.h
+++ b/include/asm-generic/preempt.h
@@ -79,11 +79,8 @@ static __always_inline bool should_resched(void)
 #ifdef CONFIG_PREEMPT
 extern asmlinkage void preempt_schedule(void);
 #define __preempt_schedule() preempt_schedule()
-
-#ifdef CONFIG_CONTEXT_TRACKING
-extern asmlinkage void preempt_schedule_context(void);
-#define __preempt_schedule_context() preempt_schedule_context()
-#endif
+extern asmlinkage void preempt_schedule_notrace(void);
+#define __preempt_schedule_notrace() preempt_schedule_notrace()
 #endif /* CONFIG_PREEMPT */
 
 #endif /* __ASM_PREEMPT_H */
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index a1a00e1..7686dd6 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -204,15 +204,11 @@ do { \
 
 #ifdef CONFIG_PREEMPT
 
-#ifndef CONFIG_CONTEXT_TRACKING
-#define __preempt_schedule_context() __preempt_schedule()
-#endif
-
 #define preempt_enable_notrace() \
 do { \
 	barrier(); \
 	if (unlikely(__preempt_count_dec_and_test())) \
-		__preempt_schedule_context(); \
+		__preempt_schedule_notrace(); \
 } while (0)
 #else
 #define preempt_enable_notrace() \
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4e925ea..af0a5a6 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2937,9 +2937,8 @@ asmlinkage __visible void __sched notrace preempt_schedule(void)
 NOKPROBE_SYMBOL(preempt_schedule);
 EXPORT_SYMBOL(preempt_schedule);
 
-#ifdef CONFIG_CONTEXT_TRACKING
 /**
- * preempt_schedule_context - preempt_schedule called by tracing
+ * preempt_schedule_notrace - preempt_schedule called by tracing
  *
  * The tracing infrastructure uses preempt_enable_notrace to prevent
  * recursion and tracing preempt enabling caused by the tracing
@@ -2952,7 +2951,7 @@ EXPORT_SYMBOL(preempt_schedule);
  * instead of preempt_schedule() to exit user context if needed before
  * calling the scheduler.
  */
-asmlinkage __visible void __sched notrace preempt_schedule_context(void)
+asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
 {
 	enum ctx_state prev_ctx;
 
@@ -2980,8 +2979,7 @@ asmlinkage __visible void __sched notrace preempt_schedule_context(void)
 		__preempt_count_sub(PREEMPT_ACTIVE + PREEMPT_DISABLE_OFFSET);
 	} while (need_resched());
 }
-EXPORT_SYMBOL_GPL(preempt_schedule_context);
-#endif /* CONFIG_CONTEXT_TRACKING */
+EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
 
 #endif /* CONFIG_PREEMPT */
 

[tip:sched/core] preempt: Reorganize the notrace definitions a bit

[tip-bot for Frederic Weisbecker]

Commit-ID:  9a92e3dc6ad02208a014d0d8404ebbd697e3d5ef
Gitweb:     http://git.kernel.org/tip/9a92e3dc6ad02208a014d0d8404ebbd697e3d5ef
Author:     Frederic Weisbecker <fweisbec@gmail.com>
AuthorDate: Thu, 4 Jun 2015 17:39:09 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Sun, 7 Jun 2015 15:57:43 +0200

preempt: Reorganize the notrace definitions a bit

preempt.h has two seperate "#ifdef CONFIG_PREEMPT" sections: one to
define preempt_enable() and another to define preempt_enable_notrace().

Lets gather both.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1433432349-1021-4-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 include/linux/preempt.h | 32 +++++++++++++++-----------------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index 7686dd6..0f1534a 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -175,48 +175,46 @@ do { \
 		__preempt_schedule(); \
 } while (0)
 
+#define preempt_enable_notrace() \
+do { \
+	barrier(); \
+	if (unlikely(__preempt_count_dec_and_test())) \
+		__preempt_schedule_notrace(); \
+} while (0)
+
 #define preempt_check_resched() \
 do { \
 	if (should_resched()) \
 		__preempt_schedule(); \
 } while (0)
 
-#else
+#else /* !CONFIG_PREEMPT */
 #define preempt_enable() \
 do { \
 	barrier(); \
 	preempt_count_dec(); \
 } while (0)
-#define preempt_check_resched() do { } while (0)
-#endif
-
-#define preempt_disable_notrace() \
-do { \
-	__preempt_count_inc(); \
-	barrier(); \
-} while (0)
 
-#define preempt_enable_no_resched_notrace() \
+#define preempt_enable_notrace() \
 do { \
 	barrier(); \
 	__preempt_count_dec(); \
 } while (0)
 
-#ifdef CONFIG_PREEMPT
+#define preempt_check_resched() do { } while (0)
+#endif /* CONFIG_PREEMPT */
 
-#define preempt_enable_notrace() \
+#define preempt_disable_notrace() \
 do { \
+	__preempt_count_inc(); \
 	barrier(); \
-	if (unlikely(__preempt_count_dec_and_test())) \
-		__preempt_schedule_notrace(); \
 } while (0)
-#else
-#define preempt_enable_notrace() \
+
+#define preempt_enable_no_resched_notrace() \
 do { \
 	barrier(); \
 	__preempt_count_dec(); \
 } while (0)
-#endif
 
 #else /* !CONFIG_PREEMPT_COUNT */