x86/tracing, x86/mm: Remove redundant trace_pagefault_key

trace_pagefault_key is used to optimize the pagefault tracepoints when it
is disabled. However, tracepoints already have built-in static_key for this
exact purpose.

Remove this redundant key.

Signed-off-by: Nam Cao <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: Gabriele Monaco <[e-mail]>
Cc: H. Peter Anvin <[e-mail]>
Cc: John Ogness <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Steven Rostedt <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]

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

···
-#ifndef _ASM_TRACE_COMMON_H
-#define _ASM_TRACE_COMMON_H
-
-#ifdef CONFIG_TRACING
-DECLARE_STATIC_KEY_FALSE(trace_pagefault_key);
-#define trace_pagefault_enabled()			\
-	static_branch_unlikely(&trace_pagefault_key)
-#else
-static inline bool trace_pagefault_enabled(void) { return false; }
-#endif
-
-#endif

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

···
 #define _TRACE_PAGE_FAULT_H
 
 #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,
 
···
 		  (void *)__entry->address, (void *)__entry->ip,
 		  __entry->error_code) );
 
-#define DEFINE_PAGE_FAULT_EVENT(name)				\
-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_pagefault_reg, trace_pagefault_unreg);
+DEFINE_EVENT(x86_exceptions, page_fault_user,
+	TP_PROTO(unsigned long address,	struct pt_regs *regs, unsigned long error_code),
+	TP_ARGS(address, regs, error_code));
 
-DEFINE_PAGE_FAULT_EVENT(page_fault_user);
-DEFINE_PAGE_FAULT_EVENT(page_fault_kernel);
+DEFINE_EVENT(x86_exceptions, page_fault_kernel,
+	TP_PROTO(unsigned long address,	struct pt_regs *regs, unsigned long error_code),
+	TP_ARGS(address, regs, error_code));
 
 #undef TRACE_INCLUDE_PATH
 #undef TRACE_INCLUDE_FILE

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

···
 #define _TRACE_IRQ_VECTORS_H
 
 #include <linux/tracepoint.h>
-#include <asm/trace/common.h>
 
 #ifdef CONFIG_X86_LOCAL_APIC
 

arch/x86/kernel/Makefile

···
 obj-$(CONFIG_UPROBES)			+= uprobes.o
 
 obj-$(CONFIG_PERF_EVENTS)		+= perf_regs.o
-obj-$(CONFIG_TRACING)			+= tracepoint.o
 obj-$(CONFIG_SCHED_MC_PRIO)		+= itmt.o
 obj-$(CONFIG_X86_UMIP)			+= umip.o
 

arch/x86/kernel/tracepoint.c

···
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Copyright (C) 2013 Seiji Aguchi <[e-mail]>
- */
-#include <linux/jump_label.h>
-#include <linux/atomic.h>
-
-#include <asm/trace/exceptions.h>
-
-DEFINE_STATIC_KEY_FALSE(trace_pagefault_key);
-
-int trace_pagefault_reg(void)
-{
-	static_branch_inc(&trace_pagefault_key);
-	return 0;
-}
-
-void trace_pagefault_unreg(void)
-{
-	static_branch_dec(&trace_pagefault_key);
-}

arch/x86/mm/fault.c

···
 trace_page_fault_entries(struct pt_regs *regs, unsigned long error_code,
 			 unsigned long address)
 {
-	if (!trace_pagefault_enabled())
-		return;
-
 	if (user_mode(regs))
 		trace_page_fault_user(address, regs, error_code);
 	else