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author | 2020-10-15 20:11:31 -0700 | |
---|---|---|
committer | 2020-10-16 11:11:20 -0700 | |
commit | e130816164e244b692921de49771eeb28205152d (patch) | |
tree | fcc0f3e2d2e7fb16ee11a9de20d8d842e9766041 /include/linux/list.h | |
parent | lib/percpu_counter.c: use helper macro abs() (diff) | |
download | linux-e130816164e244b692921de49771eeb28205152d.tar.gz linux-e130816164e244b692921de49771eeb28205152d.tar.bz2 linux-e130816164e244b692921de49771eeb28205152d.zip |
include/linux/list.h: add a macro to test if entry is pointing to the head
Add a macro to test if entry is pointing to the head of the list which is
useful in cases like:
list_for_each_entry(pos, &head, member) {
if (cond)
break;
}
if (list_entry_is_head(pos, &head, member))
return -ERRNO;
that allows to avoid additional variable to be added to track if loop has
not been stopped in the middle.
While here, convert list_for_each_entry*() family of macros to use a new one.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com>
Link: https://lkml.kernel.org/r/20200929134342.51489-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/list.h')
-rw-r--r-- | include/linux/list.h | 29 |
1 files changed, 19 insertions, 10 deletions
diff --git a/include/linux/list.h b/include/linux/list.h index 0d0d17a10d25..a18c87b63376 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -610,6 +610,15 @@ static inline void list_splice_tail_init(struct list_head *list, pos = n, n = pos->prev) /** + * list_entry_is_head - test if the entry points to the head of the list + * @pos: the type * to cursor + * @head: the head for your list. + * @member: the name of the list_head within the struct. + */ +#define list_entry_is_head(pos, head, member) \ + (&pos->member == (head)) + +/** * list_for_each_entry - iterate over list of given type * @pos: the type * to use as a loop cursor. * @head: the head for your list. @@ -617,7 +626,7 @@ static inline void list_splice_tail_init(struct list_head *list, */ #define list_for_each_entry(pos, head, member) \ for (pos = list_first_entry(head, typeof(*pos), member); \ - &pos->member != (head); \ + !list_entry_is_head(pos, head, member); \ pos = list_next_entry(pos, member)) /** @@ -628,7 +637,7 @@ static inline void list_splice_tail_init(struct list_head *list, */ #define list_for_each_entry_reverse(pos, head, member) \ for (pos = list_last_entry(head, typeof(*pos), member); \ - &pos->member != (head); \ + !list_entry_is_head(pos, head, member); \ pos = list_prev_entry(pos, member)) /** @@ -653,7 +662,7 @@ static inline void list_splice_tail_init(struct list_head *list, */ #define list_for_each_entry_continue(pos, head, member) \ for (pos = list_next_entry(pos, member); \ - &pos->member != (head); \ + !list_entry_is_head(pos, head, member); \ pos = list_next_entry(pos, member)) /** @@ -667,7 +676,7 @@ static inline void list_splice_tail_init(struct list_head *list, */ #define list_for_each_entry_continue_reverse(pos, head, member) \ for (pos = list_prev_entry(pos, member); \ - &pos->member != (head); \ + !list_entry_is_head(pos, head, member); \ pos = list_prev_entry(pos, member)) /** @@ -679,7 +688,7 @@ static inline void list_splice_tail_init(struct list_head *list, * Iterate over list of given type, continuing from current position. */ #define list_for_each_entry_from(pos, head, member) \ - for (; &pos->member != (head); \ + for (; !list_entry_is_head(pos, head, member); \ pos = list_next_entry(pos, member)) /** @@ -692,7 +701,7 @@ static inline void list_splice_tail_init(struct list_head *list, * Iterate backwards over list of given type, continuing from current position. */ #define list_for_each_entry_from_reverse(pos, head, member) \ - for (; &pos->member != (head); \ + for (; !list_entry_is_head(pos, head, member); \ pos = list_prev_entry(pos, member)) /** @@ -705,7 +714,7 @@ static inline void list_splice_tail_init(struct list_head *list, #define list_for_each_entry_safe(pos, n, head, member) \ for (pos = list_first_entry(head, typeof(*pos), member), \ n = list_next_entry(pos, member); \ - &pos->member != (head); \ + !list_entry_is_head(pos, head, member); \ pos = n, n = list_next_entry(n, member)) /** @@ -721,7 +730,7 @@ static inline void list_splice_tail_init(struct list_head *list, #define list_for_each_entry_safe_continue(pos, n, head, member) \ for (pos = list_next_entry(pos, member), \ n = list_next_entry(pos, member); \ - &pos->member != (head); \ + !list_entry_is_head(pos, head, member); \ pos = n, n = list_next_entry(n, member)) /** @@ -736,7 +745,7 @@ static inline void list_splice_tail_init(struct list_head *list, */ #define list_for_each_entry_safe_from(pos, n, head, member) \ for (n = list_next_entry(pos, member); \ - &pos->member != (head); \ + !list_entry_is_head(pos, head, member); \ pos = n, n = list_next_entry(n, member)) /** @@ -752,7 +761,7 @@ static inline void list_splice_tail_init(struct list_head *list, #define list_for_each_entry_safe_reverse(pos, n, head, member) \ for (pos = list_last_entry(head, typeof(*pos), member), \ n = list_prev_entry(pos, member); \ - &pos->member != (head); \ + !list_entry_is_head(pos, head, member); \ pos = n, n = list_prev_entry(n, member)) /** |