[fbdev] Lockdep error

3 messages, 2 authors, 2008-09-23 · open the first message on its own page

[fbdev] Lockdep error

From: Dmitry Baryshkov <hidden>
Date: 2008-09-15 12:25:12 

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>] (fbcon_blank+0x0/0x1bc) from [<c0170ea8>] (do_blank_screen+0x1e0/0x2a0)
[<c0170cc8>] (do_blank_screen+0x0/0x2a0) from [<c0154024>] (fbcon_fb_blanked+0x74/0x94)
 r5:c3967940 r4:00000001
[<c0153fb0>] (fbcon_fb_blanked+0x0/0x94) from [<c0154228>] (fbcon_event_notify+0x100/0x12c)
 r5:fffffffe r4:c39bc194
[<c0154128>] (fbcon_event_notify+0x0/0x12c) from [<c005a0d4>] (notifier_call_chain+0x38/0x7c)
[<c005a09c>] (notifier_call_chain+0x0/0x7c) from [<c005a3a0>] (__blocking_notifier_call_chain+0x54/0x6c)
 r8:c3b51ea0 r7:00000009 r6:ffffffff r5:c0427a40 r4:c0427a74
[<c005a34c>] (__blocking_notifier_call_chain+0x0/0x6c) from [<c005a3d8>] (blocking_notifier_call_chain+0x20/0x28)
 r8:00000001 r7:c3a7e000 r6:00000000 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 [<c014e450>] (store_blank+0x54/0x7c)
 r5:c38984b8 r4:c3b51ec4
[<c014e3fc>] (store_blank+0x0/0x7c) from [<c017981c>] (dev_attr_store+0x28/0x2c)
 r8:00000001 r7:c042bf80 r6:c39eba10 r5:c3967c30 r4:c38e0140
[<c01797f4>] (dev_attr_store+0x0/0x2c) from [<c00ddaac>] (flush_write_buffer+0x54/0x68)
[<c00dda58>] (flush_write_buffer+0x0/0x68) from [<c00dde08>] (sysfs_write_file+0x58/0x80)
 r8:c3b51f78 r7:c3bcb070 r6:c39eba10 r5:00000001 r4:00000001
[<c00dddb0>] (sysfs_write_file+0x0/0x80) from [<c009de04>] (vfs_write+0xb8/0x148)
[<c009dd4c>] (vfs_write+0x0/0x148) from [<c009e384>] (sys_write+0x44/0x70)
 r7:00000004 r6:c3bcb070 r5:00000000 r4:00000000
[<c009e340>] (sys_write+0x0/0x70) from [<c0025d00>] (ret_fast_syscall+0x0/0x2c)
 r6:4001b000 r5:00000001 r4:401dc658

-- 
With best wishes
Dmitry


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

From: Krzysztof Helt <hidden>
Date: 2008-09-16 21:38:52 

On Mon, 15 Sep 2008 16:21:52 +0400
Dmitry Baryshkov [off-list ref] 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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Re: [Linux-fbdev-devel] [fbdev] Lockdep error

From: Dmitry <hidden>
Date: 2008-09-23 09:53:47 

2008/9/17 Krzysztof Helt [off-list ref]:
On Mon, 15 Sep 2008 16:21:52 +0400
Dmitry Baryshkov [off-list ref] wrote:
quoted
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?
Sorry for the delay.
Yes, the patch does fix the issue for me. Thank you.
quoted hunk
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);
               }



-- 
With best wishes
Dmitry

-------------------------------------------------------------------------
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Grand prize is a trip for two to an Open Source event anywhere in the world
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