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


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