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[fbdev] Lockdep error

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[view original message]
From: Dmitry Baryshkov
Subject: [fbdev] Lockdep error
Date: Monday, September 15, 2008 - 5:21 am

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

but task is already holding lock:
 ((fb_notifier_list).rwsem){..--}, at: [<c005a384>] __blocking_notifier_call_chain+0x38/0x6c

other info that might help us debug this:
2 locks held by echo/1564:
 #0:  (&buffer->mutex){--..}, at: [<c00ddde0>] sysfs_write_file+0x30/0x80
 #1:  ((fb_notifier_list).rwsem){..--}, at: [<c005a384>] __blocking_notifier_call_chain+0x38/0x6c

stack backtrace:
[<c0029fe4>] (dump_stack+0x0/0x14) from [<c0060ce0>] (print_deadlock_bug+0xa4/0xd0)
[<c0060c3c>] (print_deadlock_bug+0x0/0xd0) from [<c0060e54>] (check_deadlock+0x148/0x17c)
 r6:c397a1e0 r5:c397a530 r4:c04fcf98
[<c0060d0c>] (check_deadlock+0x0/0x17c) from [<c00637e8>] (validate_chain+0x3c4/0x4f0)
[<c0063424>] (validate_chain+0x0/0x4f0) from [<c0063efc>] (__lock_acquire+0x5e8/0x6b4)
[<c0063914>] (__lock_acquire+0x0/0x6b4) from [<c006402c>] (lock_acquire+0x64/0x78)
[<c0063fc8>] (lock_acquire+0x0/0x78) from [<c0316ca8>] (down_read+0x4c/0x60)
 r7:00000009 r6:ffffffff r5:c0427a40 r4:c005a384
[<c0316c5c>] (down_read+0x0/0x60) from [<c005a384>] (__blocking_notifier_call_chain+0x38/0x6c)
 r5:c0427a40 r4:c0427a74
[<c005a34c>] (__blocking_notifier_call_chain+0x0/0x6c) from [<c005a3d8>] (blocking_notifier_call_chain+0x20/0x28)
 r8:00000009 r7:c086d640 r6:c3967940 r5:00000000 r4:c38984b8
[<c005a3b8>] (blocking_notifier_call_chain+0x0/0x28) from [<c014baa0>] (fb_notifier_call_chain+0x1c/0x24)
[<c014ba84>] (fb_notifier_call_chain+0x0/0x24) from [<c014c18c>] (fb_blank+0x64/0x70)
[<c014c128>] (fb_blank+0x0/0x70) from [<c0155978>] (fbcon_blank+0x114/0x1bc)
 r5:00000001 r4:c38984b8
[<c0155864>] ...
[ message continues ]
[view original message]
From: Krzysztof Helt
Subject: Re: [Linux-fbdev-devel] [fbdev] Lockdep error
Date: Tuesday, September 16, 2008 - 2:39 pm

On Mon, 15 Sep 2008 16:21:52 +0400

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);
 		}
 
--


[ message continues ]
[view original message]
From: Dmitry
Subject: Re: [Linux-fbdev-devel] [fbdev] Lockdep error
Date: Tuesday, September 23, 2008 - 2:53 am

Sorry for the delay.



-- 
With best wishes
Dmitry
--


[ message continues ]
Previous thread: [PATCH 1/1] avr32: added mem kernel command line option support by Marco Stornelli on Monday, September 15, 2008 - 3:07 am. (8 messages)

Next thread: hda_intel (sigmatel) defunct in mmotm 2008-09-13-03-09 by Jiri Slaby on Monday, September 15, 2008 - 7:00 am. (23 messages)