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[PATCH] Doc/lockdep-design: explain display of {state-bits}

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Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Jim Cromie 2006-09-30 23:27:40 -07:00 committed by Linus Torvalds
parent ce584f9138
commit fd7bcea35e
1 changed files with 22 additions and 0 deletions
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Documentation/lockdep-design.txt
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@ -36,6 +36,28 @@ The validator tracks lock-class usage history into 5 separate state bits:
- 'ever used' [ == !unused ]
When locking rules are violated, these 4 state bits are presented in the
locking error messages, inside curlies. A contrived example:
modprobe/2287 is trying to acquire lock:
(&sio_locks[i].lock){--..}, at: [<c02867fd>] mutex_lock+0x21/0x24
but task is already holding lock:
(&sio_locks[i].lock){--..}, at: [<c02867fd>] mutex_lock+0x21/0x24
The bit position indicates hardirq, softirq, hardirq-read,
softirq-read respectively, and the character displayed in each
indicates:
'.' acquired while irqs enabled
'+' acquired in irq context
'-' acquired in process context with irqs disabled
'?' read-acquired both with irqs enabled and in irq context
Unused mutexes cannot be part of the cause of an error.
Single-lock state rules:
------------------------