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Diffstat (limited to 'Documentation/lockdep-design.txt')
| -rw-r--r-- | Documentation/lockdep-design.txt | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/Documentation/lockdep-design.txt b/Documentation/lockdep-design.txt index 00d93605bfd..55a7e4fa8cc 100644 --- a/Documentation/lockdep-design.txt +++ b/Documentation/lockdep-design.txt @@ -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: ------------------------ |