RDS: Fix the atomicity for congestion map update
authorsantosh.shilimkar@oracle.com <santosh.shilimkar@oracle.com>
Thu, 14 Apr 2016 17:43:27 +0000 (10:43 -0700)
committerDavid S. Miller <davem@davemloft.net>
Sat, 16 Apr 2016 23:01:05 +0000 (19:01 -0400)
commite47db94e10447fc467777a40302f2b393e9af2fa
tree4c7df86e01d04d5ba6ec19a764807ca6b5a92261
parenta7c556546f610a331c22cb7edd9d1afe63f0cd52
RDS: Fix the atomicity for congestion map update

Two different threads with different rds sockets may be in
rds_recv_rcvbuf_delta() via receive path. If their ports
both map to the same word in the congestion map, then
using non-atomic ops to update it could cause the map to
be incorrect. Lets use atomics to avoid such an issue.

Full credit to Wengang <wen.gang.wang@oracle.com> for
finding the issue, analysing it and also pointing out
to offending code with spin lock based fix.

Reviewed-by: Leon Romanovsky <leon@leon.nu>
Signed-off-by: Wengang Wang <wen.gang.wang@oracle.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/rds/cong.c