The helper merge_and_restore_back_links() makes sure to call the caller's cmp function during the final ->prev pointer fixup, so that the cmp function may call cond_resched(). However, if the cmp function does not call cond_resched() at all, this is entirely redundant. If it does, doing at least two function calls for every two pointer assignments is a bit excessive. This patch limits the calls to once for every 256 iterations.
Signed-off-by: Rasmus Villemoes <[email protected]> --- lib/list_sort.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/lib/list_sort.c b/lib/list_sort.c index a34c78c..6b9fdaf 100644 --- a/lib/list_sort.c +++ b/lib/list_sort.c @@ -47,6 +47,7 @@ static void merge_and_restore_back_links(void *priv, struct list_head *a, struct list_head *b) { struct list_head *tail = head; + u8 count = 0; while (a && b) { /* if equal, take 'a' -- important for sort stability */ @@ -70,7 +71,8 @@ static void merge_and_restore_back_links(void *priv, * element comparison is needed, so the client's cmp() * routine can invoke cond_resched() periodically. */ - (*cmp)(priv, tail->next, tail->next); + if (unlikely(!(++count))) + (*cmp)(priv, tail->next, tail->next); tail->next->prev = tail; tail = tail->next; -- 1.9.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
