X-Git-Url: http://pileus.org/git/?a=blobdiff_plain;f=block%2Fblk-softirq.c;h=58340d0cb23a82d40edf95b77874a5781d49bcdb;hb=e33f2d238e2e53e264c758c0849423a9308eb63e;hp=475fab809a80cce9eb5573fbb392597d8dd9b838;hpb=6124a4e430b64d1577438c8648c59e996d02e73e;p=~andy%2Flinux

diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 475fab809a8..58340d0cb23 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: