[PATCH 5.4 61/67] net: thunderx: use spin_lock_bh in nicvf_set_rx_mode_task()

Greg Kroah-Hartman
2020-08-10T15:34:26Z

From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit bab9693a9a8c6dd19f670408ec1e78e12a320682 ]

A dead lock was triggered on thunderx driver:

CPU0 CPU1
---- ----
[01] lock(&(&nic->rx_mode_wq_lock)->rlock);
[11] lock(&(&mc->mca_lock)->rlock);
[12] lock(&(&nic->rx_mode_wq_lock)->rlock);
[02] <Interrupt> lock(&(&mc->mca_lock)->rlock);

The path for each is:

[01] worker_thread() -> process_one_work() -> nicvf_set_rx_mode_task()
[02] mld_ifc_timer_expire()
[11] ipv6_add_dev() -> ipv6_dev_mc_inc() -> igmp6_group_added() ->
[12] dev_mc_add() -> __dev_set_rx_mode() -> nicvf_set_rx_mode()

To fix it, it needs to disable bh on [1], so that the timer on [2]
wouldn't be triggered until rx_mode_wq_lock is released. So change
to use spin_lock_bh() instead of spin_lock().

Thanks to Paolo for helping with this.

v1->v2:
- post to netdev.

Reported-by: Rafael P. <rparrazo@redhat.com>
Tested-by: Dean Nelson <dnelson@redhat.com>
Fixes: 469998c861fa ("net: thunderx: prevent concurrent data re-writing by nicvf_set_rx_mode")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/ethernet/cavium/thunder/nicvf_main.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/net/ethernet/cavium/thunder/nicvf_main.c
+++ b/drivers/net/ethernet/cavium/thunder/nicvf_main.c
@@ -2047,11 +2047,11 @@ static void nicvf_set_rx_mode_task(struc
/* Save message data locally to prevent them from
* being overwritten by next ndo_set_rx_mode call().
*/
- spin_lock(&nic->rx_mode_wq_lock);
+ spin_lock_bh(&nic->rx_mode_wq_lock);
mode = vf_work->mode;
mc = vf_work->mc;
vf_work->mc = NULL;
- spin_unlock(&nic->rx_mode_wq_lock);
+ spin_unlock_bh(&nic->rx_mode_wq_lock);

__nicvf_set_rx_mode_task(mode, mc, nic);
}