ring-buffer: use generic version of in_nmi

Impact: clean up

Now that a generic in_nmi is available, this patch removes the
special code in the ring_buffer and implements the in_nmi generic
version instead.

With this change, I was also able to rename the "arch_ftrace_nmi_enter"
back to "ftrace_nmi_enter" and remove the code from the ring buffer.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 918073c6681b5da6e3c1e862fdfb2946ac354d42..d74d75e0952d4a680b7bec08f51bb9731bdac2a7 100644 (file)
--- 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 arch_ftrace_nmi_enter(void)
+void ftrace_nmi_enter(void)
 {
        atomic_inc(&nmi_running);
        /* Must have nmi_running seen before reading write flag */
@@ -124,7 +124,7 @@ void arch_ftrace_nmi_enter(void)
        }
 }
 
-void arch_ftrace_nmi_exit(void)
+void ftrace_nmi_exit(void)
 {
        /* Finish all executions before clearing nmi_running */
        smp_wmb();

diff --git a/include/linux/ftrace_irq.h b/include/linux/ftrace_irq.h
index 29de6779a96380f5a3a64bbed27c6c4b8ec03efe..dca7bf8cffe2f48f0d9f91be301013ca45a709b2 100644 (file)
--- a/include/linux/ftrace_irq.h
+++ b/include/linux/ftrace_irq.h
@@ -3,14 +3,6 @@
 
 
 #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/ring_buffer.c b/kernel/trace/ring_buffer.c
index a60a6a852f4285a15191f5b9bbfa34f661ade832..5ee344417cd50b627202ee2b04adffbbad85b453 100644 (file)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -8,6 +8,7 @@
 #include <linux/spinlock.h>
 #include <linux/debugfs.h>
 #include <linux/uaccess.h>
+#include <linux/hardirq.h>
 #include <linux/module.h>
 #include <linux/percpu.h>
 #include <linux/mutex.h>
@@ -19,35 +20,6 @@
 
 #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
@@ -1027,12 +999,23 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
 
                local_irq_save(flags);
                /*
+                * 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.
+                *
                 * 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 (unlikely(in_nmi())) {
                        if (!__raw_spin_trylock(&cpu_buffer->lock))
                                goto out_unlock;
                } else