Commit fd7bcea3 authored by Jim Cromie's avatar Jim Cromie Committed by Linus Torvalds
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[PATCH] Doc/lockdep-design: explain display of {state-bits}

Signed-off-by: default avatarJim Cromie <>
Cc: Ingo Molnar <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent ce584f91
......@@ -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
'.' 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:
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