1 files changed, 8 insertions, 0 deletions

diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 475fab809a80..58340d0cb23a 100644
--- a/block/blk-softirq.c
+++ b/block/blk-softirq.c
@@ -124,6 +124,14 @@ void __blk_complete_request(struct request *req)
         } else
                 ccpu = cpu;
 
+        /*
+         * If current CPU and requested CPU are in the same group, running
+         * softirq in current CPU. One might concern this is just like
+         * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is
+         * running in interrupt handler, and currently I/O controller doesn't
+         * support multiple interrupts, so current CPU is unique actually. This
+         * avoids IPI sending from current CPU to the first CPU of a group.
+         */
         if (ccpu == cpu || ccpu == group_cpu) {
                 struct list_head *list;
 do_local: