| Message ID | 1445041610-30133-1-git-send-email-santosh.shilimkar@oracle.com |
|---|---|
| State | Superseded, archived |
| Delegated to: | David Miller |
| Headers | show |
On (10/16/15 20:26), Santosh Shilimkar wrote: > > diff --git a/net/rds/send.c b/net/rds/send.c > + if (!test_bit(RDS_LL_SEND_FULL, &conn->c_flags)) > + queue_delayed_work(rds_wq, &conn->c_send_w, 0); A minor note- it would help to add some comments here explaining that the pong has already been added to the sendq earlier.. in the case of IB, if RDS_LL_SEND_FULL has been set, it takes some head-scratching to figure out how the pong gets sent, and a few comments could help clarify that. but other than that, the contents look good to me, thus Acked-by: Sowmini Varadhan <sowmini.varadhan@oracle.com> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 10/16/2015 6:45 PM, Sowmini Varadhan wrote: > On (10/16/15 20:26), Santosh Shilimkar wrote: >> >> diff --git a/net/rds/send.c b/net/rds/send.c >> + if (!test_bit(RDS_LL_SEND_FULL, &conn->c_flags)) >> + queue_delayed_work(rds_wq, &conn->c_send_w, 0); > > A minor note- it would help to add some comments here explaining > that the pong has already been added to the sendq earlier.. > in the case of IB, if RDS_LL_SEND_FULL has been set, it takes some > head-scratching to figure out how the pong gets sent, and a few > comments could help clarify that. > Right. The check confused you. I will update the patch and drop the check all together and add a jiffies for the queuing which should take care of it. Will post v2 with that update. > but other than that, the contents look good to me, thus > > Acked-by: Sowmini Varadhan <sowmini.varadhan@oracle.com> > Thanks !! regards, Santosh -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/rds/send.c b/net/rds/send.c index ee49c25..7a377a1 100644 --- a/net/rds/send.c +++ b/net/rds/send.c @@ -1182,9 +1182,8 @@ rds_send_pong(struct rds_connection *conn, __be16 dport) rds_stats_inc(s_send_queued); rds_stats_inc(s_send_pong); - ret = rds_send_xmit(conn); - if (ret == -ENOMEM || ret == -EAGAIN) - queue_delayed_work(rds_wq, &conn->c_send_w, 1); + if (!test_bit(RDS_LL_SEND_FULL, &conn->c_flags)) + queue_delayed_work(rds_wq, &conn->c_send_w, 0); rds_message_put(rm); return 0;
Sowmini found hang with rds-ping while testing RDS over TCP. Its a corner case and doesn't happen always. The issue is not reproducible with IB transport. Its clear from below dump why we see it with RDS TCP. [<ffffffff8153b7e5>] do_tcp_setsockopt+0xb5/0x740 [<ffffffff8153bec4>] tcp_setsockopt+0x24/0x30 [<ffffffff814d57d4>] sock_common_setsockopt+0x14/0x20 [<ffffffffa096071d>] rds_tcp_xmit_prepare+0x5d/0x70 [rds_tcp] [<ffffffffa093b5f7>] rds_send_xmit+0xd7/0x740 [rds] [<ffffffffa093bda2>] rds_send_pong+0x142/0x180 [rds] [<ffffffffa0939d34>] rds_recv_incoming+0x274/0x330 [rds] [<ffffffff810815ae>] ? ttwu_queue+0x11e/0x130 [<ffffffff814dcacd>] ? skb_copy_bits+0x6d/0x2c0 [<ffffffffa0960350>] rds_tcp_data_recv+0x2f0/0x3d0 [rds_tcp] [<ffffffff8153d836>] tcp_read_sock+0x96/0x1c0 [<ffffffffa0960060>] ? rds_tcp_recv_init+0x40/0x40 [rds_tcp] [<ffffffff814d6a90>] ? sock_def_write_space+0xa0/0xa0 [<ffffffffa09604d1>] rds_tcp_data_ready+0xa1/0xf0 [rds_tcp] [<ffffffff81545249>] tcp_data_queue+0x379/0x5b0 [<ffffffffa0960cdb>] ? rds_tcp_write_space+0xbb/0x110 [rds_tcp] [<ffffffff81547fd2>] tcp_rcv_established+0x2e2/0x6e0 [<ffffffff81552602>] tcp_v4_do_rcv+0x122/0x220 [<ffffffff81553627>] tcp_v4_rcv+0x867/0x880 [<ffffffff8152e0b3>] ip_local_deliver_finish+0xa3/0x220 This happens because rds_send_xmit() chain wants to take sock_lock which is already taken by tcp_v4_rcv() on its way to rds_tcp_data_ready(). Commit db6526dcb51b ("RDS: use rds_send_xmit() state instead of RDS_LL_SEND_FULL") which was trying to opportunistically finish the send request in same thread context. But because of above recursive lock hang with RDS TCP, the send work from rds_send_pong() needs to deferred to worker to avoid lock up. Given RDS ping is more of connectivity test than performance critical path, its should be ok even for transport like IB. Reported-by: Sowmini Varadhan <sowmini.varadhan@oracle.com> Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com> --- net/rds/send.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)