diff options
| -rw-r--r-- | arch/x86/Kconfig | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/ftrace.c | 8 | ||||
| -rw-r--r-- | include/linux/ftrace_irq.h | 10 | ||||
| -rw-r--r-- | kernel/trace/Kconfig | 8 | ||||
| -rw-r--r-- | kernel/trace/ring_buffer.c | 48 |
5 files changed, 68 insertions, 7 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 73f7fe8fd4d1..a6be725cb049 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -34,6 +34,7 @@ config X86 select HAVE_FUNCTION_TRACER select HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_TRACE_MCOUNT_TEST + select HAVE_FTRACE_NMI_ENTER if DYNAMIC_FTRACE || FUNCTION_GRAPH_TRACER select HAVE_KVM if ((X86_32 && !X86_VOYAGER && !X86_VISWS && !X86_NUMAQ) || X86_64) select HAVE_ARCH_KGDB if !X86_VOYAGER select HAVE_ARCH_TRACEHOOK diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 4d33224c055f..4c683587055b 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -113,7 +113,7 @@ static void ftrace_mod_code(void) MCOUNT_INSN_SIZE); } -void ftrace_nmi_enter(void) +void arch_ftrace_nmi_enter(void) { atomic_inc(&in_nmi); /* Must have in_nmi seen before reading write flag */ @@ -124,7 +124,7 @@ void ftrace_nmi_enter(void) } } -void ftrace_nmi_exit(void) +void arch_ftrace_nmi_exit(void) { /* Finish all executions before clearing in_nmi */ smp_wmb(); @@ -376,12 +376,12 @@ int ftrace_disable_ftrace_graph_caller(void) */ static atomic_t in_nmi; -void ftrace_nmi_enter(void) +void arch_ftrace_nmi_enter(void) { atomic_inc(&in_nmi); } -void ftrace_nmi_exit(void) +void arch_ftrace_nmi_exit(void) { atomic_dec(&in_nmi); } diff --git a/include/linux/ftrace_irq.h b/include/linux/ftrace_irq.h index 366a054d0b05..29de6779a963 100644 --- a/include/linux/ftrace_irq.h +++ b/include/linux/ftrace_irq.h @@ -2,7 +2,15 @@ #define _LINUX_FTRACE_IRQ_H -#if defined(CONFIG_DYNAMIC_FTRACE) || defined(CONFIG_FUNCTION_GRAPH_TRACER) +#ifdef CONFIG_FTRACE_NMI_ENTER +extern void arch_ftrace_nmi_enter(void); +extern void arch_ftrace_nmi_exit(void); +#else +static inline void arch_ftrace_nmi_enter(void) { } +static inline void arch_ftrace_nmi_exit(void) { } +#endif + +#ifdef CONFIG_RING_BUFFER extern void ftrace_nmi_enter(void); extern void ftrace_nmi_exit(void); #else diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index 28f2644484d9..25131a5d5e4f 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -9,6 +9,9 @@ config USER_STACKTRACE_SUPPORT config NOP_TRACER bool +config HAVE_FTRACE_NMI_ENTER + bool + config HAVE_FUNCTION_TRACER bool @@ -37,6 +40,11 @@ config TRACER_MAX_TRACE config RING_BUFFER bool +config FTRACE_NMI_ENTER + bool + depends on HAVE_FTRACE_NMI_ENTER + default y + config TRACING bool select DEBUG_FS diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index b36d7374ceef..a60a6a852f42 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -4,6 +4,7 @@ * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com> */ #include <linux/ring_buffer.h> +#include <linux/ftrace_irq.h> #include <linux/spinlock.h> #include <linux/debugfs.h> #include <linux/uaccess.h> @@ -19,6 +20,35 @@ #include "trace.h" /* + * Since the write to the buffer is still not fully lockless, + * we must be careful with NMIs. The locks in the writers + * are taken when a write crosses to a new page. The locks + * protect against races with the readers (this will soon + * be fixed with a lockless solution). + * + * Because we can not protect against NMIs, and we want to + * keep traces reentrant, we need to manage what happens + * when we are in an NMI. + */ +static DEFINE_PER_CPU(int, rb_in_nmi); + +void ftrace_nmi_enter(void) +{ + __get_cpu_var(rb_in_nmi)++; + /* call arch specific handler too */ + arch_ftrace_nmi_enter(); +} + +void ftrace_nmi_exit(void) +{ + arch_ftrace_nmi_exit(); + __get_cpu_var(rb_in_nmi)--; + /* NMIs are not recursive */ + WARN_ON_ONCE(__get_cpu_var(rb_in_nmi)); +} + + +/* * A fast way to enable or disable all ring buffers is to * call tracing_on or tracing_off. Turning off the ring buffers * prevents all ring buffers from being recorded to. @@ -982,6 +1012,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer *buffer = cpu_buffer->buffer; struct ring_buffer_event *event; unsigned long flags; + bool lock_taken = false; commit_page = cpu_buffer->commit_page; /* we just need to protect against interrupts */ @@ -995,7 +1026,19 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page *next_page = tail_page; local_irq_save(flags); - __raw_spin_lock(&cpu_buffer->lock); + /* + * NMIs can happen after we take the lock. + * If we are in an NMI, only take the lock + * if it is not already taken. Otherwise + * simply fail. + */ + if (unlikely(__get_cpu_var(rb_in_nmi))) { + if (!__raw_spin_trylock(&cpu_buffer->lock)) + goto out_unlock; + } else + __raw_spin_lock(&cpu_buffer->lock); + + lock_taken = true; rb_inc_page(cpu_buffer, &next_page); @@ -1097,7 +1140,8 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, if (tail <= BUF_PAGE_SIZE) local_set(&tail_page->write, tail); - __raw_spin_unlock(&cpu_buffer->lock); + if (likely(lock_taken)) + __raw_spin_unlock(&cpu_buffer->lock); local_irq_restore(flags); return NULL; } |