bus: skip useless iterations in find function

The starting point is known. The iterator can be directly set to it.

The function rte_bus_find can easily be used with a comparison function
always returning True. This would make it a regular bus iterator.

Users doing so would however accomplish such iteration in

   O(N * N/2) = O(N^2)

Which can be avoided.

Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>

diff --git a/lib/librte_eal/common/eal_common_bus.c b/lib/librte_eal/common/eal_common_bus.c
index c3c77f4..5c63ced 100644 (file)
--- a/lib/librte_eal/common/eal_common_bus.c
+++ b/lib/librte_eal/common/eal_common_bus.c
@@ -146,15 +146,16 @@ struct rte_bus *
 rte_bus_find(const struct rte_bus *start, rte_bus_cmp_t cmp,
             const void *data)
 {
-       struct rte_bus *bus = NULL;
+       struct rte_bus *bus;
 
-       TAILQ_FOREACH(bus, &rte_bus_list, next) {
-               if (start && bus == start) {
-                       start = NULL; /* starting point found */
-                       continue;
-               }
+       if (start != NULL)
+               bus = TAILQ_NEXT(start, next);
+       else
+               bus = TAILQ_FIRST(&rte_bus_list);
+       while (bus != NULL) {
                if (cmp(bus, data) == 0)
                        break;
+               bus = TAILQ_NEXT(bus, next);
        }
        return bus;
 }