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-rw-r--r--block/blk-softirq.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 475fab809a80..1366a89d8e66 100644
--- a/block/blk-softirq.c
+++ b/block/blk-softirq.c
@@ -115,7 +115,7 @@ void __blk_complete_request(struct request *req)
/*
* Select completion CPU
*/
- if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) && req->cpu != -1) {
+ if (req->cpu != -1) {
ccpu = req->cpu;
if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags)) {
ccpu = blk_cpu_to_group(ccpu);
@@ -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: