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authorHåkon Bugge <Haakon.Bugge@oracle.com>2017-07-20 12:28:55 +0200
committerDavid S. Miller <davem@davemloft.net>2017-07-20 15:33:01 -0700
commite623a48ee433985f6ca0fb238f0002cc2eccdf53 (patch)
treee3dc5acbe886b14e0dde4296b6b78748ac7175cd /net
parent070f9c658a59f9a736b1c040001d37b0952e778e (diff)
downloadblackbird-op-linux-e623a48ee433985f6ca0fb238f0002cc2eccdf53.tar.gz
blackbird-op-linux-e623a48ee433985f6ca0fb238f0002cc2eccdf53.zip
rds: Make sure updates to cp_send_gen can be observed
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 <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>
Diffstat (limited to 'net')
-rw-r--r--net/rds/send.c6
1 files changed, 3 insertions, 3 deletions
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;
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