x86/tracing: Disentangle pagefault and resched IPI tracing key

The pagefault and the resched IPI handler are the only ones where it is
worth to optimize the code further in case tracepoints are disabled. But it
makes no sense to have a single static key for both.

Seperate the static keys so the facilities are handled seperately.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170828064957.536699116@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/trace/common.h

@@ -1,15 +1,16 @@
 #ifndef _ASM_TRACE_COMMON_H
 #define _ASM_TRACE_COMMON_H
 
-extern int trace_irq_vector_regfunc(void);
-extern void trace_irq_vector_unregfunc(void);
-
 #ifdef CONFIG_TRACING
-DECLARE_STATIC_KEY_FALSE(trace_irqvectors_key);
-#define trace_irqvectors_enabled()			\
-	static_branch_unlikely(&trace_irqvectors_key)
+DECLARE_STATIC_KEY_FALSE(trace_pagefault_key);
+#define trace_pagefault_enabled()			\
+	static_branch_unlikely(&trace_pagefault_key)
+DECLARE_STATIC_KEY_FALSE(trace_resched_ipi_key);
+#define trace_resched_ipi_enabled()			\
+	static_branch_unlikely(&trace_resched_ipi_key)
 #else
-static inline bool trace_irqvectors_enabled(void) { return false; }
+static inline bool trace_pagefault_enabled(void) { return false; }
+static inline bool trace_resched_ipi_enabled(void) { return false; }
 #endif
 
 #endif

arch/x86/include/asm/trace/exceptions.h

@@ -7,6 +7,9 @@
 #include <linux/tracepoint.h>
 #include <asm/trace/common.h>
 
+extern int trace_pagefault_reg(void);
+extern void trace_pagefault_unreg(void);
+
 DECLARE_EVENT_CLASS(x86_exceptions,
 
 	TP_PROTO(unsigned long address, struct pt_regs *regs,
@@ -35,8 +38,7 @@ DEFINE_EVENT_FN(x86_exceptions, name,				\
 	TP_PROTO(unsigned long address,	struct pt_regs *regs,	\
 		 unsigned long error_code),			\
 	TP_ARGS(address, regs, error_code),			\
-	trace_irq_vector_regfunc,				\
-	trace_irq_vector_unregfunc);
+	trace_pagefault_reg, trace_pagefault_unreg);
 
 DEFINE_PAGE_FAULT_EVENT(page_fault_user);
 DEFINE_PAGE_FAULT_EVENT(page_fault_kernel);

arch/x86/include/asm/trace/irq_vectors.h

@@ -7,6 +7,9 @@
 #include <linux/tracepoint.h>
 #include <asm/trace/common.h>
 
+extern int trace_resched_ipi_reg(void);
+extern void trace_resched_ipi_unreg(void);
+
 DECLARE_EVENT_CLASS(x86_irq_vector,
 
 	TP_PROTO(int vector),
@@ -24,17 +27,24 @@ DECLARE_EVENT_CLASS(x86_irq_vector,
 	TP_printk("vector=%d", __entry->vector) );
 
 #define DEFINE_IRQ_VECTOR_EVENT(name)		\
+DEFINE_EVENT_FN(x86_irq_vector, name##_entry,	\
+	TP_PROTO(int vector),			\
+	TP_ARGS(vector), NULL, NULL);		\
+DEFINE_EVENT_FN(x86_irq_vector, name##_exit,	\
+	TP_PROTO(int vector),			\
+	TP_ARGS(vector), NULL, NULL);
+
+#define DEFINE_RESCHED_IPI_EVENT(name)		\
 DEFINE_EVENT_FN(x86_irq_vector, name##_entry,	\
 	TP_PROTO(int vector),			\
 	TP_ARGS(vector),			\
-	trace_irq_vector_regfunc,		\
-	trace_irq_vector_unregfunc);		\
+	trace_resched_ipi_reg,			\
+	trace_resched_ipi_unreg);		\
 DEFINE_EVENT_FN(x86_irq_vector, name##_exit,	\
 	TP_PROTO(int vector),			\
 	TP_ARGS(vector),			\
-	trace_irq_vector_regfunc,		\
-	trace_irq_vector_unregfunc);
-
+	trace_resched_ipi_reg,			\
+	trace_resched_ipi_unreg);
 
 /*
  * local_timer - called when entering/exiting a local timer interrupt
@@ -42,10 +52,17 @@ DEFINE_EVENT_FN(x86_irq_vector, name##_exit,	\
  */
 DEFINE_IRQ_VECTOR_EVENT(local_timer);
 
+/*
+ * The ifdef is required because that tracepoint macro hell emits tracepoint
+ * code in files which include this header even if the tracepoint is not
+ * enabled. Brilliant stuff that.
+ */
+#ifdef CONFIG_SMP
 /*
  * reschedule - called when entering/exiting a reschedule vector handler
  */
-DEFINE_IRQ_VECTOR_EVENT(reschedule);
+DEFINE_RESCHED_IPI_EVENT(reschedule);
+#endif
 
 /*
  * spurious_apic - called when entering/exiting a spurious apic vector handler

arch/x86/kernel/smp.c

@@ -262,7 +262,7 @@ __visible void __irq_entry smp_reschedule_interrupt(struct pt_regs *regs)
 	ack_APIC_irq();
 	inc_irq_stat(irq_resched_count);
 
-	if (trace_irqvectors_enabled()) {
+	if (trace_resched_ipi_enabled()) {
 		/*
 		 * scheduler_ipi() might call irq_enter() as well, but
 		 * nested calls are fine.

arch/x86/kernel/tracepoint.c

@@ -10,15 +10,32 @@
 #include <asm/hw_irq.h>
 #include <asm/desc.h>
 
-DEFINE_STATIC_KEY_FALSE(trace_irqvectors_key);
+DEFINE_STATIC_KEY_FALSE(trace_pagefault_key);
 
-int trace_irq_vector_regfunc(void)
+int trace_pagefault_reg(void)
 {
-	static_branch_inc(&trace_irqvectors_key);
+	static_branch_inc(&trace_pagefault_key);
 	return 0;
 }
 
-void trace_irq_vector_unregfunc(void)
+void trace_pagefault_unreg(void)
 {
-	static_branch_dec(&trace_irqvectors_key);
+	static_branch_dec(&trace_pagefault_key);
 }
+
+#ifdef CONFIG_SMP
+
+DEFINE_STATIC_KEY_FALSE(trace_resched_ipi_key);
+
+int trace_resched_ipi_reg(void)
+{
+	static_branch_inc(&trace_resched_ipi_key);
+	return 0;
+}
+
+void trace_resched_ipi_unreg(void)
+{
+	static_branch_dec(&trace_resched_ipi_key);
+}
+
+#endif

arch/x86/mm/fault.c

@@ -1510,7 +1510,7 @@ do_page_fault(struct pt_regs *regs, unsigned long error_code)
 	enum ctx_state prev_state;
 
 	prev_state = exception_enter();
-	if (trace_irqvectors_enabled())
+	if (trace_pagefault_enabled())
 		trace_page_fault_entries(address, regs, error_code);
 
 	__do_page_fault(regs, error_code, address);