linux-kernel - [PATCH 1/3] vgacon: Fix & cleanup refcounting

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Date:	Tue, 13 May 2014 12:09:27 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Jiri Slaby <jslaby@...e.cz>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] vgacon: Fix & cleanup refcounting

The vgacon driver prepares a two element array of uni_pagedir_loc and
uses the second item as its own reference counter for sharing the
uni_pagedir.  And the code assumes blindly that the second item is
available if the assigned vc_uni_pagedir isn't the standard one, which
might be wrong (although currently it's so).

This patch fixes that wrong assumption, and gives a slight cleanup
along with it: namely, instead of array, just give the uni_pagedir_loc
and a separate refcount variable.  It makes the code a bit more
understandable at first glance.

Signed-off-by: Takashi Iwai <tiwai@...e.de>
---
 drivers/video/console/vgacon.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index 9d8feac67637..9e18770aaba6 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -87,7 +87,8 @@ static void vgacon_save_screen(struct vc_data *c);
 static int vgacon_scroll(struct vc_data *c, int t, int b, int dir,
 			 int lines);
 static void vgacon_invert_region(struct vc_data *c, u16 * p, int count);
-static unsigned long vgacon_uni_pagedir[2];
+static unsigned long vgacon_uni_pagedir;
+static int vgacon_refcount;
 
 /* Description of the hardware situation */
 static int		vga_init_done		__read_mostly;
@@ -575,12 +576,12 @@ static void vgacon_init(struct vc_data *c, int init)
 	if (vga_512_chars)
 		c->vc_hi_font_mask = 0x0800;
 	p = *c->vc_uni_pagedir_loc;
-	if (c->vc_uni_pagedir_loc == &c->vc_uni_pagedir ||
-	    !--c->vc_uni_pagedir_loc[1])
+	if (c->vc_uni_pagedir_loc != &vgacon_uni_pagedir) {
 		con_free_unimap(c);
-	c->vc_uni_pagedir_loc = vgacon_uni_pagedir;
-	vgacon_uni_pagedir[1]++;
-	if (!vgacon_uni_pagedir[0] && p)
+		c->vc_uni_pagedir_loc = &vgacon_uni_pagedir;
+		vgacon_refcount++;
+	}
+	if (!vgacon_uni_pagedir && p)
 		con_set_default_unimap(c);
 
 	/* Only set the default if the user didn't deliberately override it */
@@ -597,7 +598,7 @@ static void vgacon_deinit(struct vc_data *c)
 		vga_set_mem_top(c);
 	}
 
-	if (!--vgacon_uni_pagedir[1])
+	if (!--vgacon_refcount)
 		con_free_unimap(c);
 	c->vc_uni_pagedir_loc = &c->vc_uni_pagedir;
 	con_set_default_unimap(c);
-- 
1.9.2

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