linux-kernel - [RFC PATCH 09/14] ring_buffer: Initialize completions statically in the benchmark

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Message-Id: <1438094371-8326-10-git-send-email-pmladek@suse.com>
Date:	Tue, 28 Jul 2015 16:39:26 +0200
From:	Petr Mladek <pmladek@...e.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Josh Triplett <josh@...htriplett.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>, Borislav Petkov <bp@...e.de>,
	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	Vlastimil Babka <vbabka@...e.cz>,
	live-patching@...r.kernel.org, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org, Petr Mladek <pmladek@...e.com>
Subject: [RFC PATCH 09/14] ring_buffer: Initialize completions statically in the benchmark

It looks strange to initialize the completions repeatedly.

This patch uses static initialization. It simplifies the code
and even helps to get rid of two memory barriers.

Signed-off-by: Petr Mladek <pmladek@...e.com>
---
 kernel/trace/ring_buffer_benchmark.c | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c
index a1503a027ee2..ccb1a0b95f64 100644
--- a/kernel/trace/ring_buffer_benchmark.c
+++ b/kernel/trace/ring_buffer_benchmark.c
@@ -24,8 +24,8 @@ struct rb_page {
 static int wakeup_interval = 100;
 
 static int reader_finish;
-static struct completion read_start;
-static struct completion read_done;
+static DECLARE_COMPLETION(read_start);
+static DECLARE_COMPLETION(read_done);
 
 static struct ring_buffer *buffer;
 static struct task_struct *producer;
@@ -270,11 +270,6 @@ static void ring_buffer_producer(void)
 	trace_printk("End ring buffer hammer\n");
 
 	if (consumer) {
-		/* Init both completions here to avoid races */
-		init_completion(&read_start);
-		init_completion(&read_done);
-		/* the completions must be visible before the finish var */
-		smp_wmb();
 		reader_finish = 1;
 		/* finish var visible before waking up the consumer */
 		smp_wmb();
@@ -389,13 +384,10 @@ static int ring_buffer_consumer_thread(void *arg)
 
 static int ring_buffer_producer_thread(void *arg)
 {
-	init_completion(&read_start);
-
 	while (!kthread_should_stop() && !kill_test) {
 		ring_buffer_reset(buffer);
 
 		if (consumer) {
-			smp_wmb();
 			wake_up_process(consumer);
 			wait_for_completion(&read_start);
 		}
-- 
1.8.5.6

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