From fd7bcea35e7efb108c34ee2b3840942a3749cadb Mon Sep 17 00:00:00 2001 From: Jim Cromie Date: Sat, 30 Sep 2006 23:27:40 -0700 Subject: [PATCH] Doc/lockdep-design: explain display of {state-bits} Signed-off-by: Jim Cromie Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/lockdep-design.txt | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/Documentation/lockdep-design.txt b/Documentation/lockdep-design.txt index 00d93605bfd3..55a7e4fa8cc2 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: [] mutex_lock+0x21/0x24 + + but task is already holding lock: + (&sio_locks[i].lock){--..}, at: [] 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: ------------------------ -- cgit v1.2.3