Commit 126f760c authored Sep 06, 2017 by Håkon Bugge Committed by David S. Miller Sep 07, 2017

rds: Fix incorrect statistics counting



In rds_send_xmit() there is logic to batch the sends. However, if
another thread has acquired the lock and has incremented the send_gen,
it is considered a race and we yield. The code incrementing the
s_send_lock_queue_raced statistics counter did not count this event
correctly.

This commit counts the race condition correctly.

Changes from v1:
- Removed check for *someone_on_xmit()*
- Fixed incorrect indentation

Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
Reviewed-by: Knut Omang <knut.omang@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent eef5a7cc

net/rds/send.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -428,14 +428,18 @@ int rds_send_xmit(struct rds_conn_path *cp)
		* some work and we will skip our goto
		*/
		if (ret == 0) {
		bool raced;

		smp_mb();
		raced = send_gen != READ_ONCE(cp->cp_send_gen);

		if ((test_bit(0, &conn->c_map_queued) \|\|
		!list_empty(&cp->cp_send_queue)) &&
		send_gen == READ_ONCE(cp->cp_send_gen)) {
		rds_stats_inc(s_send_lock_queue_raced);
		!list_empty(&cp->cp_send_queue)) && !raced) {
		if (batch_count < send_batch_count)
		goto restart;
		queue_delayed_work(rds_wq, &cp->cp_send_w, 1);
		} else if (raced) {
		rds_stats_inc(s_send_lock_queue_raced);
		}
		}
		out: