use mutex instead of semaphore in virtual console driver

The virtual console driver uses a semaphore as mutex.  Use the mutex API
instead of the (binary) semaphore.
Signed-off-by: Matthias Kaehlcke <matthias.kaehlcke@gmail.com>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/vc_screen.c

@@ -28,11 +28,13 @@
 #include <linux/interrupt.h>
 #include <linux/mm.h>
 #include <linux/init.h>
+#include <linux/mutex.h>
 #include <linux/vt_kern.h>
 #include <linux/selection.h>
 #include <linux/kbd_kern.h>
 #include <linux/console.h>
 #include <linux/device.h>
+
 #include <asm/uaccess.h>
 #include <asm/byteorder.h>
 #include <asm/unaligned.h>
@@ -69,11 +71,11 @@ static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
 {
 	int size;
 
-	down(&con_buf_sem);
+	mutex_lock(&con_buf_mtx);
 	size = vcs_size(file->f_path.dentry->d_inode);
 	switch (orig) {
 		default:
-			up(&con_buf_sem);
+			mutex_unlock(&con_buf_mtx);
 			return -EINVAL;
 		case 2:
 			offset += size;
@@ -84,11 +86,11 @@ static loff_t vcs_lseek(struct file *file, loff_t offset, int orig)
 			break;
 	}
 	if (offset < 0 || offset > size) {
-		up(&con_buf_sem);
+		mutex_unlock(&con_buf_mtx);
 		return -EINVAL;
 	}
 	file->f_pos = offset;
-	up(&con_buf_sem);
+	mutex_unlock(&con_buf_mtx);
 	return file->f_pos;
 }
 
@@ -105,7 +107,7 @@ vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 	unsigned short *org = NULL;
 	ssize_t ret;
 
-	down(&con_buf_sem);
+	mutex_lock(&con_buf_mtx);
 
 	pos = *ppos;
 
@@ -262,7 +264,7 @@ vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 		ret = read;
 unlock_out:
 	release_console_sem();
-	up(&con_buf_sem);
+	mutex_unlock(&con_buf_mtx);
 	return ret;
 }
 
@@ -279,7 +281,7 @@ vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 	u16 *org0 = NULL, *org = NULL;
 	size_t ret;
 
-	down(&con_buf_sem);
+	mutex_lock(&con_buf_mtx);
 
 	pos = *ppos;
 
@@ -449,7 +451,7 @@ vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 unlock_out:
 	release_console_sem();
 
-	up(&con_buf_sem);
+	mutex_unlock(&con_buf_mtx);
 
 	return ret;
 }

drivers/char/vt.c

@@ -86,6 +86,7 @@
 #include <linux/mm.h>
 #include <linux/console.h>
 #include <linux/init.h>
+#include <linux/mutex.h>
 #include <linux/vt_kern.h>
 #include <linux/selection.h>
 #include <linux/tiocl.h>
@@ -1952,7 +1953,7 @@ static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, int c)
  * kernel memory allocation is available.
  */
 char con_buf[CON_BUF_SIZE];
-DECLARE_MUTEX(con_buf_sem);
+DEFINE_MUTEX(con_buf_mtx);
 
 /* is_double_width() is based on the wcwidth() implementation by
  * Markus Kuhn -- 2003-05-20 (Unicode 4.0)
@@ -2049,7 +2050,7 @@ static int do_con_write(struct tty_struct *tty, const unsigned char *buf, int co
 
 	/* At this point 'buf' is guaranteed to be a kernel buffer
 	 * and therefore no access to userspace (and therefore sleeping)
-	 * will be needed.  The con_buf_sem serializes all tty based
+	 * will be needed.  The con_buf_mtx serializes all tty based
 	 * console rendering and vcs write/read operations.  We hold
 	 * the console spinlock during the entire write.
 	 */

include/linux/vt_kern.h

@@ -9,6 +9,7 @@
 #include <linux/vt.h>
 #include <linux/kd.h>
 #include <linux/tty.h>
+#include <linux/mutex.h>
 #include <linux/console_struct.h>
 #include <linux/mm.h>
 
@@ -82,7 +83,7 @@ void reset_vc(struct vc_data *vc);
 
 #define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE)
 extern char con_buf[CON_BUF_SIZE];
-extern struct semaphore con_buf_sem;
+extern struct mutex con_buf_mtx;
 extern char vt_dont_switch;
 
 struct vt_spawn_console {