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Subject[tip: sched/core] preempt/dynamic: Provide preempt_schedule[_notrace]() static calls
The following commit has been merged into the sched/core branch of tip:

Commit-ID: 8c98e8cf723c3ab2ac924b0942dd3b8074f874e5
Gitweb: https://git.kernel.org/tip/8c98e8cf723c3ab2ac924b0942dd3b8074f874e5
Author: Peter Zijlstra (Intel) <peterz@infradead.org>
AuthorDate: Mon, 18 Jan 2021 15:12:21 +01:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 05 Feb 2021 17:19:57 +01:00

preempt/dynamic: Provide preempt_schedule[_notrace]() static calls

Provide static calls to control preempt_schedule[_notrace]()
(called in CONFIG_PREEMPT) so that we can override their behaviour when
preempt= is overriden.

Since the default behaviour is full preemption, both their calls are
initialized to the arch provided wrapper, if any.

[fweisbec: only define static calls when PREEMPT_DYNAMIC, make it less
dependent on x86 with __preempt_schedule_func]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210118141223.123667-7-frederic@kernel.org
---
arch/x86/include/asm/preempt.h | 34 +++++++++++++++++++++++++--------
kernel/sched/core.c | 12 ++++++++++++-
2 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
index 69485ca..9b12dce 100644
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -5,6 +5,7 @@
#include <asm/rmwcc.h>
#include <asm/percpu.h>
#include <linux/thread_info.h>
+#include <linux/static_call_types.h>

DECLARE_PER_CPU(int, __preempt_count);

@@ -103,16 +104,33 @@ static __always_inline bool should_resched(int preempt_offset)
}

#ifdef CONFIG_PREEMPTION
- extern asmlinkage void preempt_schedule_thunk(void);
-# define __preempt_schedule() \
- asm volatile ("call preempt_schedule_thunk" : ASM_CALL_CONSTRAINT)

- extern asmlinkage void preempt_schedule(void);
- extern asmlinkage void preempt_schedule_notrace_thunk(void);
-# define __preempt_schedule_notrace() \
- asm volatile ("call preempt_schedule_notrace_thunk" : ASM_CALL_CONSTRAINT)
+extern asmlinkage void preempt_schedule(void);
+extern asmlinkage void preempt_schedule_thunk(void);
+
+#define __preempt_schedule_func preempt_schedule_thunk
+
+DECLARE_STATIC_CALL(preempt_schedule, __preempt_schedule_func);
+
+#define __preempt_schedule() \
+do { \
+ __ADDRESSABLE(STATIC_CALL_KEY(preempt_schedule)); \
+ asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule) : ASM_CALL_CONSTRAINT); \
+} while (0)
+
+extern asmlinkage void preempt_schedule_notrace(void);
+extern asmlinkage void preempt_schedule_notrace_thunk(void);
+
+#define __preempt_schedule_notrace_func preempt_schedule_notrace_thunk
+
+DECLARE_STATIC_CALL(preempt_schedule_notrace, __preempt_schedule_notrace_func);
+
+#define __preempt_schedule_notrace() \
+do { \
+ __ADDRESSABLE(STATIC_CALL_KEY(preempt_schedule_notrace)); \
+ asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule_notrace) : ASM_CALL_CONSTRAINT); \
+} while (0)

- extern asmlinkage void preempt_schedule_notrace(void);
#endif

#endif /* __ASM_PREEMPT_H */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index bc7b00b..cd0c46f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5251,6 +5251,12 @@ asmlinkage __visible void __sched notrace preempt_schedule(void)
NOKPROBE_SYMBOL(preempt_schedule);
EXPORT_SYMBOL(preempt_schedule);

+#ifdef CONFIG_PREEMPT_DYNAMIC
+DEFINE_STATIC_CALL(preempt_schedule, __preempt_schedule_func);
+EXPORT_STATIC_CALL(preempt_schedule);
+#endif
+
+
/**
* preempt_schedule_notrace - preempt_schedule called by tracing
*
@@ -5303,6 +5309,12 @@ asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
}
EXPORT_SYMBOL_GPL(preempt_schedule_notrace);

+#ifdef CONFIG_PREEMPT_DYNAMIC
+DEFINE_STATIC_CALL(preempt_schedule_notrace, __preempt_schedule_notrace_func);
+EXPORT_STATIC_CALL(preempt_schedule_notrace);
+#endif
+
+
#endif /* CONFIG_PREEMPTION */

/*
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