commit 1b959e18c4d6b4b981f887260b0f8e7939efa411
author Steven Rostedt <srostedt@redhat.com> Thu Sep 03 10:12:13 2009 -0400
committer Steven Rostedt <rostedt@goodmis.org> Fri Sep 04 11:25:27 2009 -0400
tree 3f7b9950cfe19742cfe04bc3feb11f7ad0a46e71
parent 98277991a99734f3a31d638afb47d4484ac73e43

ring-buffer: remove unnecessary cpu_relax

The loops in the ring buffer that use cpu_relax are not dependent on
other CPUs. They simply came across some padding in the ring buffer and
are skipping over them. It is a normal loop and does not require a
cpu_relax.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/ring_buffer.c

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 2878bd43..a05541a 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -3132,10 +3132,8 @@
 		spin_unlock(&cpu_buffer->reader_lock);
 	local_irq_restore(flags);
 
-	if (event && event->type_len == RINGBUF_TYPE_PADDING) {
-		cpu_relax();
+	if (event && event->type_len == RINGBUF_TYPE_PADDING)
 		goto again;
-	}
 
 	return event;
 }
@@ -3160,10 +3158,8 @@
 	event = rb_iter_peek(iter, ts);
 	spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
 
-	if (event && event->type_len == RINGBUF_TYPE_PADDING) {
-		cpu_relax();
+	if (event && event->type_len == RINGBUF_TYPE_PADDING)
 		goto again;
-	}
 
 	return event;
 }
@@ -3209,10 +3205,8 @@
  out:
 	preempt_enable();
 
-	if (event && event->type_len == RINGBUF_TYPE_PADDING) {
-		cpu_relax();
+	if (event && event->type_len == RINGBUF_TYPE_PADDING)
 		goto again;
-	}
 
 	return event;
 }
@@ -3302,10 +3296,8 @@
  out:
 	spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
 
-	if (event && event->type_len == RINGBUF_TYPE_PADDING) {
-		cpu_relax();
+	if (event && event->type_len == RINGBUF_TYPE_PADDING)
 		goto again;
-	}
 
 	return event;
 }