1 files changed, 13 insertions, 3 deletions

diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 487addc85bb5..58340d0cb23a 100644
--- a/block/blk-softirq.c
+++ b/block/blk-softirq.c
@@ -103,7 +103,7 @@ static struct notifier_block __cpuinitdata blk_cpu_notifier = {
 
 void __blk_complete_request(struct request *req)
 {
-        int ccpu, cpu;
+        int ccpu, cpu, group_cpu = NR_CPUS;
         struct request_queue *q = req->q;
         unsigned long flags;
 
@@ -117,12 +117,22 @@ void __blk_complete_request(struct request *req)
          */
         if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) && req->cpu != -1) {
                 ccpu = req->cpu;
-                if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
+                if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags)) {
                         ccpu = blk_cpu_to_group(ccpu);
+                        group_cpu = blk_cpu_to_group(cpu);
+                }
         } else
                 ccpu = cpu;
 
-        if (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:
                 list = &__get_cpu_var(blk_cpu_done);