From e623a48ee433985f6ca0fb238f0002cc2eccdf53 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?H=C3=A5kon=20Bugge?= Date: Thu, 20 Jul 2017 12:28:55 +0200 Subject: rds: Make sure updates to cp_send_gen can be observed MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit cp->cp_send_gen is treated as a normal variable, although it may be used by different threads. This is fixed by using {READ,WRITE}_ONCE when it is incremented and READ_ONCE when it is read outside the {acquire,release}_in_xmit protection. Normative reference from the Linux-Kernel Memory Model: Loads from and stores to shared (but non-atomic) variables should be protected with the READ_ONCE(), WRITE_ONCE(), and ACCESS_ONCE(). Clause 5.1.2.4/25 in the C standard is also relevant. Signed-off-by: Håkon Bugge Reviewed-by: Knut Omang Acked-by: Santosh Shilimkar Signed-off-by: David S. Miller --- net/rds/send.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'net/rds/send.c') diff --git a/net/rds/send.c b/net/rds/send.c index e81aa176f4e2..41b9f0f5bb9c 100644 --- a/net/rds/send.c +++ b/net/rds/send.c @@ -170,8 +170,8 @@ restart: * The acquire_in_xmit() check above ensures that only one * caller can increment c_send_gen at any time. */ - cp->cp_send_gen++; - send_gen = cp->cp_send_gen; + send_gen = READ_ONCE(cp->cp_send_gen) + 1; + WRITE_ONCE(cp->cp_send_gen, send_gen); /* * rds_conn_shutdown() sets the conn state and then tests RDS_IN_XMIT, @@ -431,7 +431,7 @@ over_batch: smp_mb(); if ((test_bit(0, &conn->c_map_queued) || !list_empty(&cp->cp_send_queue)) && - send_gen == cp->cp_send_gen) { + send_gen == READ_ONCE(cp->cp_send_gen)) { rds_stats_inc(s_send_lock_queue_raced); if (batch_count < send_batch_count) goto restart; -- cgit v1.2.3