linux-kernel - [RFC][PATCH v3 2/4] printk: do not console_cont

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Message-Id: <1453536913-9545-3-git-send-email-sergey.senozhatsky@gmail.com>
Date:	Sat, 23 Jan 2016 17:15:11 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Petr Mladek <pmladek@...e.com>, Jan Kara <jack@...e.com>,
	Tejun Heo <tj@...nel.org>, Kyle McMartin <kyle@...nel.org>,
	Dave Jones <davej@...emonkey.org.uk>,
	Calvin Owens <calvinowens@...com>,
	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: [RFC][PATCH v3 2/4] printk: do not console_cont_flush() on every jump to again

Every jump to `again' label will call console_cont_flush(),
which is not really something big -- it just adds one extra
raw_spin_lock_irqsave/raw_spin_unlock_irqrestore. However, to
keep the previous behaviour we can call console_cont_flush()
only when `retry' is false -- which happens once, all jumps
to `again' label have `retry' set to true.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
---
 kernel/printk/printk.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index c39232a..dc722fc 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2213,7 +2213,7 @@ void console_unlock(void)
 	static u64 seen_seq;
 	unsigned long flags;
 	bool wake_klogd = false;
-	bool do_cond_resched, retry;
+	bool do_cond_resched, retry = false;
 
 	if (console_suspended) {
 		up_console_sem();
@@ -2246,7 +2246,8 @@ again:
 	}
 
 	/* flush buffered message fragment immediately to console */
-	console_cont_flush(text, sizeof(text));
+	if (!retry)
+		console_cont_flush(text, sizeof(text));
 
 	for (;;) {
 		struct printk_log *msg;
-- 
2.7.0