Commit-ID: 2feb1b316d48004d905278c02a55902cab0be8be Gitweb: http://git.kernel.org/tip/2feb1b316d48004d905278c02a55902cab0be8be Author: Thomas Gleixner <t...@linutronix.de> AuthorDate: Mon, 28 Aug 2017 08:47:21 +0200 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Tue, 29 Aug 2017 11:42:23 +0200
x86/tracing: Introduce a static key for exception tracing Switching the IDT just for avoiding tracepoints creates a completely impenetrable macro/inline/ifdef mess. There is no point in avoiding tracepoints for most of the traps/exceptions. For the more expensive tracepoints, like pagefaults, this can be handled with an explicit static key. Preparatory patch to remove the tracing IDT. Signed-off-by: Thomas Gleixner <t...@linutronix.de> Cc: Andy Lutomirski <l...@kernel.org> Cc: Borislav Petkov <b...@alien8.de> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Steven Rostedt <rost...@goodmis.org> Link: http://lkml.kernel.org/r/20170828064956.593094...@linutronix.de Signed-off-by: Ingo Molnar <mi...@kernel.org> --- arch/x86/include/asm/trace/common.h | 15 +++++++++++++++ arch/x86/include/asm/trace/exceptions.h | 4 +--- arch/x86/include/asm/trace/irq_vectors.h | 4 +--- arch/x86/kernel/tracepoint.c | 9 ++++++++- 4 files changed, 25 insertions(+), 7 deletions(-) diff --git a/arch/x86/include/asm/trace/common.h b/arch/x86/include/asm/trace/common.h new file mode 100644 index 0000000..b1eb7b1 --- /dev/null +++ b/arch/x86/include/asm/trace/common.h @@ -0,0 +1,15 @@ +#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) +#else +static inline bool trace_irqvectors_enabled(void) { return false; } +#endif + +#endif diff --git a/arch/x86/include/asm/trace/exceptions.h b/arch/x86/include/asm/trace/exceptions.h index 2422b14..960a5b5 100644 --- a/arch/x86/include/asm/trace/exceptions.h +++ b/arch/x86/include/asm/trace/exceptions.h @@ -5,9 +5,7 @@ #define _TRACE_PAGE_FAULT_H #include <linux/tracepoint.h> - -extern int trace_irq_vector_regfunc(void); -extern void trace_irq_vector_unregfunc(void); +#include <asm/trace/common.h> DECLARE_EVENT_CLASS(x86_exceptions, diff --git a/arch/x86/include/asm/trace/irq_vectors.h b/arch/x86/include/asm/trace/irq_vectors.h index 32dd6a9..7825b44 100644 --- a/arch/x86/include/asm/trace/irq_vectors.h +++ b/arch/x86/include/asm/trace/irq_vectors.h @@ -5,9 +5,7 @@ #define _TRACE_IRQ_VECTORS_H #include <linux/tracepoint.h> - -extern int trace_irq_vector_regfunc(void); -extern void trace_irq_vector_unregfunc(void); +#include <asm/trace/common.h> DECLARE_EVENT_CLASS(x86_irq_vector, diff --git a/arch/x86/kernel/tracepoint.c b/arch/x86/kernel/tracepoint.c index 1551513..dd4aa04 100644 --- a/arch/x86/kernel/tracepoint.c +++ b/arch/x86/kernel/tracepoint.c @@ -4,9 +4,11 @@ * Copyright (C) 2013 Seiji Aguchi <seiji.agu...@hds.com> * */ +#include <linux/jump_label.h> +#include <linux/atomic.h> + #include <asm/hw_irq.h> #include <asm/desc.h> -#include <linux/atomic.h> atomic_t trace_idt_ctr = ATOMIC_INIT(0); struct desc_ptr trace_idt_descr = { NR_VECTORS * 16 - 1, @@ -15,6 +17,7 @@ struct desc_ptr trace_idt_descr = { NR_VECTORS * 16 - 1, /* No need to be aligned, but done to keep all IDTs defined the same way. */ gate_desc trace_idt_table[NR_VECTORS] __page_aligned_bss; +DEFINE_STATIC_KEY_FALSE(trace_irqvectors_key); static int trace_irq_vector_refcount; static DEFINE_MUTEX(irq_vector_mutex); @@ -36,6 +39,8 @@ static void switch_idt(void *arg) int trace_irq_vector_regfunc(void) { + static_branch_inc(&trace_irqvectors_key); + mutex_lock(&irq_vector_mutex); if (!trace_irq_vector_refcount) { set_trace_idt_ctr(1); @@ -49,6 +54,8 @@ int trace_irq_vector_regfunc(void) void trace_irq_vector_unregfunc(void) { + static_branch_dec(&trace_irqvectors_key); + mutex_lock(&irq_vector_mutex); trace_irq_vector_refcount--; if (!trace_irq_vector_refcount) {
