diff options
author | Steven Whitehouse <swhiteho@redhat.com> | 2006-07-17 09:25:26 -0400 |
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committer | Steven Whitehouse <swhiteho@redhat.com> | 2006-07-17 09:25:26 -0400 |
commit | 4bf311ddfbffe12d41ad1a3c311ab727db6f72cb (patch) | |
tree | 9d19a2774e83637d86dc876f3af22af1dacf0bec /include/linux/rwsem.h | |
parent | 597d0cae0f99f62501e229bed50e8149604015bb (diff) | |
parent | 82d6897fefca6206bca7153805b4c5359ce97fc4 (diff) |
Merge branch 'master'
Diffstat (limited to 'include/linux/rwsem.h')
-rw-r--r-- | include/linux/rwsem.h | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h index 658afb37c3f..7b524b4109a 100644 --- a/include/linux/rwsem.h +++ b/include/linux/rwsem.h @@ -61,12 +61,25 @@ extern void downgrade_write(struct rw_semaphore *sem); #ifdef CONFIG_DEBUG_LOCK_ALLOC /* - * nested locking: + * nested locking. NOTE: rwsems are not allowed to recurse + * (which occurs if the same task tries to acquire the same + * lock instance multiple times), but multiple locks of the + * same lock class might be taken, if the order of the locks + * is always the same. This ordering rule can be expressed + * to lockdep via the _nested() APIs, but enumerating the + * subclasses that are used. (If the nesting relationship is + * static then another method for expressing nested locking is + * the explicit definition of lock class keys and the use of + * lockdep_set_class() at lock initialization time. + * See Documentation/lockdep-design.txt for more details.) */ extern void down_read_nested(struct rw_semaphore *sem, int subclass); extern void down_write_nested(struct rw_semaphore *sem, int subclass); /* - * Take/release a lock when not the owner will release it: + * Take/release a lock when not the owner will release it. + * + * [ This API should be avoided as much as possible - the + * proper abstraction for this case is completions. ] */ extern void down_read_non_owner(struct rw_semaphore *sem); extern void up_read_non_owner(struct rw_semaphore *sem); |