From ae4efd9cdffde2e0bb4d06c99121f389346ec9a2 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Wed, 22 Jun 2011 11:20:09 +0200
Subject: [PATCH] --- yaml --- r: 256996 b: refs/heads/master c:
 4f2a8d3cf5e0486fd547633fa86c5d130ae98cad h: refs/heads/master v: v3

---
 [refs]                |  2 +-
 trunk/kernel/printk.c | 20 ++++++++++++++++++--
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/[refs] b/[refs]
index 0a08e389639a..867e543e1c5c 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 0b5e1c5255e7ee8670e077e8224e5c2281229a5b
+refs/heads/master: 4f2a8d3cf5e0486fd547633fa86c5d130ae98cad
diff --git a/trunk/kernel/printk.c b/trunk/kernel/printk.c
index 751e7b84e9e3..37dff3429adb 100644
--- a/trunk/kernel/printk.c
+++ b/trunk/kernel/printk.c
@@ -1244,7 +1244,7 @@ void console_unlock(void)
 {
 	unsigned long flags;
 	unsigned _con_start, _log_end;
-	unsigned wake_klogd = 0;
+	unsigned wake_klogd = 0, retry = 0;
 
 	if (console_suspended) {
 		up(&console_sem);
@@ -1253,6 +1253,7 @@ void console_unlock(void)
 
 	console_may_schedule = 0;
 
+again:
 	for ( ; ; ) {
 		spin_lock_irqsave(&logbuf_lock, flags);
 		wake_klogd |= log_start - log_end;
@@ -1273,8 +1274,23 @@ void console_unlock(void)
 	if (unlikely(exclusive_console))
 		exclusive_console = NULL;
 
-	spin_unlock_irqrestore(&logbuf_lock, flags);
+	spin_unlock(&logbuf_lock);
+
 	up(&console_sem);
+
+	/*
+	 * Someone could have filled up the buffer again, so re-check if there's
+	 * something to flush. In case we cannot trylock the console_sem again,
+	 * there's a new owner and the console_unlock() from them will do the
+	 * flush, no worries.
+	 */
+	spin_lock(&logbuf_lock);
+	if (con_start != log_end)
+		retry = 1;
+	spin_unlock_irqrestore(&logbuf_lock, flags);
+	if (retry && console_trylock())
+		goto again;
+
 	if (wake_klogd)
 		wake_up_klogd();
 }