From 126f760ca94dae77425695f9f9238b731de86e32 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?H=C3=A5kon=20Bugge?= Date: Wed, 6 Sep 2017 18:35:51 +0200 Subject: [PATCH] rds: Fix incorrect statistics counting MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Knut Omang Acked-by: Santosh Shilimkar Signed-off-by: David S. Miller --- net/rds/send.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/net/rds/send.c b/net/rds/send.c index 058a40743041..b52cdc8ae428 100644 --- a/net/rds/send.c +++ b/net/rds/send.c @@ -428,14 +428,18 @@ over_batch: * 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: