linux-kernel - Re: [Linux-fbdev-devel] [fbdev] Lockdep error

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Date:	Tue, 16 Sep 2008 23:39:16 +0200
From:	Krzysztof Helt <krzysztof.h1@...pl>
To:	Dmitry Baryshkov <dbaryshkov@...il.com>
Cc:	linux-fbdev-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, rpurdie@...ys.net, adaplas@...il.com
Subject: Re: [Linux-fbdev-devel] [fbdev] Lockdep error

On Mon, 15 Sep 2008 16:21:52 +0400
Dmitry Baryshkov <dbaryshkov@...il.com> wrote:

> Hi,
> 
> After doing
> # echo 1 > /sys/class/graphics/fb0/blank
> I got the following in my kernel log:
> 
> =============================================
> [ INFO: possible recursive locking detected ]
> 2.6.27-rc6-00086-gda63874-dirty #97
> ---------------------------------------------
> echo/1564 is trying to acquire lock:
>  ((fb_notifier_list).rwsem){..--}, at: [<c005a384>] __blocking_notifier_call_chain+0x38/0x6c
> 

Does the patch below fix the problem for you?

Kind regards,
Krzysztof

diff -urp linux-ref/drivers/video/console/fbcon.c linux-mm/drivers/video/console/fbcon.c
--- linux-ref/drivers/video/console/fbcon.c	2008-09-05 23:38:47.000000000 +0200
+++ linux-mm/drivers/video/console/fbcon.c	2008-09-16 23:30:52.309604454 +0200
@@ -2400,11 +2400,15 @@ static int fbcon_blank(struct vc_data *v
 
  	if (!fbcon_is_inactive(vc, info)) {
 		if (ops->blank_state != blank) {
+			int ret = 1;
+
 			ops->blank_state = blank;
 			fbcon_cursor(vc, blank ? CM_ERASE : CM_DRAW);
 			ops->cursor_flash = (!blank);
 
-			if (fb_blank(info, blank))
+			if (info->fbops->fb_blank)
+				ret = info->fbops->fb_blank(blank, info);
+			if (ret)
 				fbcon_generic_blank(vc, info, blank);
 		}
 
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