Fix infinite recursive notifier in the fbdev layer. This causes recursive locking. Dmitry Baryshkov found the problem and confirmed that the patch fixes the bug. 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 Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl> Reported-by: Dmitry Baryshkov <dbaryshkov@gmail.com> Testted-by: Dmitry Baryshkov <dbaryshkov@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Krzysztof Helt