From: Kunhoon Baik <knhoon.baik@samsung.com>
Date: Wed, 30 Mar 2016 08:59:31 +0000 (+0900)
Subject: avoid not-allowable mutex lock condition
X-Git-Tag: submit/tizen/20160407.093933~1
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=refs%2Fchanges%2F34%2F64334%2F3;p=platform%2Fkernel%2Flinux-exynos.git

avoid not-allowable mutex lock condition

Change-Id: Icd2c90535687558aa3f294471edb865ef178a5b4
Signed-off-by: Kazimierz Krosman <k.krosman@samsung.com>
---

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 5b8304ded867..2a38f63adf43 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -943,7 +943,6 @@ static ssize_t kmsg_read(struct log_buffer *log_b, struct file *file,
 			ret = wait_event_interruptible(log_b->wait,
 						user->seq != log_b->next_seq);
 		} else {
-			rcu_read_unlock();
 			kref_get(&log_b->refcount);
 			ret = wait_event_interruptible(log_b->wait,
 						user->seq != log_b->next_seq);
@@ -951,7 +950,6 @@ static ssize_t kmsg_read(struct log_buffer *log_b, struct file *file,
 				ret = -ENXIO;
 			if (kref_put(&log_b->refcount, log_buf_release))
 				ret = -ENXIO;
-			rcu_read_lock();
 		}
 		if (ret)
 			goto out;
@@ -1056,6 +1054,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 	ssize_t ret = -ENXIO;
 	int minor = iminor(file->f_inode);
 	struct log_buffer *log_b;
+	int found = 0;
 
 	if (!user)
 		return -EBADF;
@@ -1066,11 +1065,17 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 	rcu_read_lock();
 	list_for_each_entry_rcu(log_b, &log_buf.list, list) {
 		if (log_b->minor == minor) {
-			ret = kmsg_read(log_b, file, buf, count, ppos);
+			found = 1;
+			kref_get(&log_b->refcount);
 			break;
 		}
 	}
 	rcu_read_unlock();
+
+	if(found){
+		ret = kmsg_read(log_b, file, buf, count, ppos);
+		kref_put(&log_b->refcount, log_buf_release);
+	}
 	return ret;
 }
 
@@ -1210,6 +1215,7 @@ static int devkmsg_open(struct inode *inode, struct file *file)
 	int ret = -ENXIO;
 	int minor = iminor(file->f_inode);
 	struct log_buffer *log_b;
+	int found = 0;
 
 	/* write-only does not need any file context */
 	if ((file->f_flags & O_ACCMODE) == O_WRONLY)
@@ -1227,11 +1233,17 @@ static int devkmsg_open(struct inode *inode, struct file *file)
 	rcu_read_lock();
 	list_for_each_entry_rcu(log_b, &log_buf.list, list) {
 		if (log_b->minor == minor) {
-			ret = kmsg_open(log_b, file);
+			found = 1;
+			kref_get(&log_b->refcount);
 			break;
 		}
 	}
 	rcu_read_unlock();
+
+	if(found){
+		ret = kmsg_open(log_b, file);
+		kref_put(&log_b->refcount, log_buf_release);
+	}
 	return ret;
 }