diff options
Diffstat (limited to 'Documentation/lockdep-design.txt')
-rw-r--r-- | Documentation/lockdep-design.txt | 30 |
1 files changed, 17 insertions, 13 deletions
diff --git a/Documentation/lockdep-design.txt b/Documentation/lockdep-design.txt index 488773018152..938ea22f2cc0 100644 --- a/Documentation/lockdep-design.txt +++ b/Documentation/lockdep-design.txt | |||
@@ -27,33 +27,37 @@ lock-class. | |||
27 | State | 27 | State |
28 | ----- | 28 | ----- |
29 | 29 | ||
30 | The validator tracks lock-class usage history into 5 separate state bits: | 30 | The validator tracks lock-class usage history into 4n + 1 separate state bits: |
31 | 31 | ||
32 | - 'ever held in hardirq context' [ == hardirq-safe ] | 32 | - 'ever held in STATE context' |
33 | - 'ever held in softirq context' [ == softirq-safe ] | 33 | - 'ever head as readlock in STATE context' |
34 | - 'ever held with hardirqs enabled' [ == hardirq-unsafe ] | 34 | - 'ever head with STATE enabled' |
35 | - 'ever held with softirqs and hardirqs enabled' [ == softirq-unsafe ] | 35 | - 'ever head as readlock with STATE enabled' |
36 | |||
37 | Where STATE can be either one of (kernel/lockdep_states.h) | ||
38 | - hardirq | ||
39 | - softirq | ||
40 | - reclaim_fs | ||
36 | 41 | ||
37 | - 'ever used' [ == !unused ] | 42 | - 'ever used' [ == !unused ] |
38 | 43 | ||
39 | When locking rules are violated, these 4 state bits are presented in the | 44 | When locking rules are violated, these state bits are presented in the |
40 | locking error messages, inside curlies. A contrived example: | 45 | locking error messages, inside curlies. A contrived example: |
41 | 46 | ||
42 | modprobe/2287 is trying to acquire lock: | 47 | modprobe/2287 is trying to acquire lock: |
43 | (&sio_locks[i].lock){--..}, at: [<c02867fd>] mutex_lock+0x21/0x24 | 48 | (&sio_locks[i].lock){-.-...}, at: [<c02867fd>] mutex_lock+0x21/0x24 |
44 | 49 | ||
45 | but task is already holding lock: | 50 | but task is already holding lock: |
46 | (&sio_locks[i].lock){--..}, at: [<c02867fd>] mutex_lock+0x21/0x24 | 51 | (&sio_locks[i].lock){-.-...}, at: [<c02867fd>] mutex_lock+0x21/0x24 |
47 | 52 | ||
48 | 53 | ||
49 | The bit position indicates hardirq, softirq, hardirq-read, | 54 | The bit position indicates STATE, STATE-read, for each of the states listed |
50 | softirq-read respectively, and the character displayed in each | 55 | above, and the character displayed in each indicates: |
51 | indicates: | ||
52 | 56 | ||
53 | '.' acquired while irqs disabled | 57 | '.' acquired while irqs disabled |
54 | '+' acquired in irq context | 58 | '+' acquired in irq context |
55 | '-' acquired with irqs enabled | 59 | '-' acquired with irqs enabled |
56 | '?' read acquired in irq context with irqs enabled. | 60 | '?' acquired in irq context with irqs enabled. |
57 | 61 | ||
58 | Unused mutexes cannot be part of the cause of an error. | 62 | Unused mutexes cannot be part of the cause of an error. |
59 | 63 | ||