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>

1 files changed, 13 insertions, 30 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index a60a6a852f42..5ee344417cd5 100644
--- 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>
@@ -20,35 +21,6 @@
 #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
  * prevents all ring buffers from being recorded to.
@@ -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