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Date:   Tue,  4 Aug 2020 15:02:30 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     network dev <netdev@...r.kernel.org>
Cc:     davem@...emloft.net, dnelson@...hat.com,
        linux-arm-kernel@...ts.infradead.org,
        Sunil Goutham <sgoutham@...ium.com>,
        Robert Richter <rric@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Subject: [PATCHv2 net] net: thunderx: use spin_lock_bh in nicvf_set_rx_mode_task()

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@...hat.com>
Tested-by: Dean Nelson <dnelson@...hat.com>
Fixes: 469998c861fa ("net: thunderx: prevent concurrent data re-writing by nicvf_set_rx_mode")
Signed-off-by: Xin Long <lucien.xin@...il.com>
---
 drivers/net/ethernet/cavium/thunder/nicvf_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/cavium/thunder/nicvf_main.c b/drivers/net/ethernet/cavium/thunder/nicvf_main.c
index 2ba0ce1..a82c708 100644
--- a/drivers/net/ethernet/cavium/thunder/nicvf_main.c
+++ b/drivers/net/ethernet/cavium/thunder/nicvf_main.c
@@ -2042,11 +2042,11 @@ static void nicvf_set_rx_mode_task(struct work_struct *work_arg)
 	/* 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);
 }
-- 
2.1.0

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