diff options
| author | Andrew Morton <akpm@osdl.org> | 2003-12-29 05:52:48 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@home.osdl.org> | 2003-12-29 05:52:48 -0800 |
| commit | 3182fe922bfe643b496950feb9e037d237125954 (patch) | |
| tree | 8db6759df50b6ac8a04a09e3c699718f1c026635 /include/linux/list.h | |
| parent | c13bb4092eaad8ab8aeee575d97dafa8dab0c915 (diff) | |
[PATCH] list_empty_careful() documentation.
From: Ingo Molnar <mingo@elte.hu>
I'd also suggest the following patch below, to clarify the use of
unsynchronized list_empty(). list_empty_careful() can only be safe in the
very specific case of "one-shot" list entries which might be removed by
another CPU. (but nothing else can happen to them and this is their only
final state.) list_empty_careful() is otherwise completely unsynchronized
on both the compiler and CPU level and is not 'SMP safe' in any way.
Diffstat (limited to 'include/linux/list.h')
| -rw-r--r-- | include/linux/list.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/list.h b/include/linux/list.h index 0835011b0ffb..9a5df31af22e 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -212,6 +212,12 @@ static inline int list_empty(const struct list_head *head) * list_empty_careful - tests whether a list is * empty _and_ checks that no other CPU might be * in the process of still modifying either member + * + * NOTE: using list_empty_careful() without synchronization + * can only be safe if the only activity that can happen + * to the list entry is list_del_init(). Eg. it cannot be used + * if another CPU could re-list_add() it. + * * @head: the list to test. */ static inline int list_empty_careful(const struct list_head *head) |