linux-kernel - [PATCH][GIT PULL] ring-buffer: Place duplicate expression into a single function

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Date:	Wed, 01 Sep 2010 12:49:52 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Neil Brown <neilb@...e.de>,
	"John W. Linville" <linville@...driver.com>,
	"ksummit-2010-discuss@...ts.linux-foundation.org" 
	<ksummit-2010-discuss@...ts.linux-foundation.org>
Subject: [PATCH][GIT PULL] ring-buffer: Place duplicate expression into a
 single function


Ingo,

Please pull the latest tip/perf/core tree, which can be found at:

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
tip/perf/core


Steven Rostedt (1):
      ring-buffer: Place duplicate expression into a single function

----
 kernel/trace/ring_buffer.c |   21 +++++++++++++++------
 1 files changed, 15 insertions(+), 6 deletions(-)
---------------------------
commit f6195aa09e618d712f52bf4fa33b5293820eb93d
Author: Steven Rostedt <srostedt@...hat.com>
Date:   Wed Sep 1 12:23:12 2010 -0400

    ring-buffer: Place duplicate expression into a single function
    
    While discussing the strictness of the 80 character limit on the
    Kernel Summit Discussion mailing list, I showed examples that I
    broke that limit slightly with some algorithms. In discussing with
    John Linville, what looked better, I realized that two of the
    80 char breaking culprits were an identical expression.
    
    As a clean up, this patch moves the identical expression into its
    own helper function and that is used instead. As a side effect,
    the offending code is now under the 80 character limit. :-)
    
    This clean up code also changes the expression from
    
    	(A - B) - C  to  A - (B + C)
    
    This makes the code look a little nicer too.
    
    Cc: John W. Linville <linville@...driver.com>
    Signed-off-by: Steven Rostedt <rostedt@...dmis.org>

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 19cccc3..ef27017 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2606,6 +2606,19 @@ void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
 }
 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
 
+/*
+ * The total entries in the ring buffer is the running counter
+ * of entries entered into the ring buffer, minus the sum of
+ * the entries read from the ring buffer and the number of
+ * entries that were overwritten.
+ */
+static inline unsigned long
+rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
+{
+	return local_read(&cpu_buffer->entries) -
+		(local_read(&cpu_buffer->overrun) + cpu_buffer->read);
+}
+
 /**
  * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
  * @buffer: The ring buffer
@@ -2614,16 +2627,13 @@ EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
 unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
 {
 	struct ring_buffer_per_cpu *cpu_buffer;
-	unsigned long ret;
 
 	if (!cpumask_test_cpu(cpu, buffer->cpumask))
 		return 0;
 
 	cpu_buffer = buffer->buffers[cpu];
-	ret = (local_read(&cpu_buffer->entries) - local_read(&cpu_buffer->overrun))
-		- cpu_buffer->read;
 
-	return ret;
+	return rb_num_of_entries(cpu_buffer);
 }
 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
 
@@ -2684,8 +2694,7 @@ unsigned long ring_buffer_entries(struct ring_buffer *buffer)
 	/* if you care about this being correct, lock the buffer */
 	for_each_buffer_cpu(buffer, cpu) {
 		cpu_buffer = buffer->buffers[cpu];
-		entries += (local_read(&cpu_buffer->entries) -
-			    local_read(&cpu_buffer->overrun)) - cpu_buffer->read;
+		entries += rb_num_of_entries(cpu_buffer);
 	}
 
 	return entries;


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