[RFC PATCH 10/11] printk: survive rotation of sequence numbers

From: Petr Mladek <pmladek@suse.cz>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Dave Anderson <anderson@redhat.com>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Kay Sievers <kay@vrfy.org>, Jiri Kosina <jkosina@suse.cz>,
	Michal Hocko <mhocko@suse.cz>, Jan Kara <jack@suse.cz>,
	linux-kernel@vger.kernel.org, Petr Mladek <pmladek@suse.cz>
Subject: [RFC PATCH 10/11] printk: survive rotation of sequence numbers
Date: Fri,  9 May 2014 11:11:04 +0200	[thread overview]
Message-ID: <1399626665-29817-11-git-send-email-pmladek@suse.cz> (raw)
In-Reply-To: <1399626665-29817-1-git-send-email-pmladek@suse.cz>

NMI log buffer uses half of "unsigned long" to store the sequence number.
The maximum value might be relatively small, especially on 32-bit systems.
This patch makes the check for free space more strict, so it does give
false results after the rotation.

Signed-off-by: Petr Mladek <pmladek@suse.cz>
---
 kernel/printk/printk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 874ebab41ba3..9c97b6daccc3 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -540,7 +540,7 @@ static int log_make_free_space(struct printk_log *log, u32 msg_size)
 	int freed = 0;
 	int ret = 0;
 
-	while (get_first_seq(log) < get_next_seq(log)) {
+	while (get_first_seq(log) != get_next_seq(log)) {
 		if (logbuf_has_space(log, msg_size, false))
 			goto out;
 
-- 
1.8.4

