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From 32a72bee7a275f47c235fdb36249703c892ce8d8 Mon Sep 17 00:00:00 2001
Message-Id: <32a72bee7a275f47c235fdb36249703c892ce8d8.1531335939.git.jan.steffens@gmail.com>
In-Reply-To: <a2d2476ffec7d988b1a5396586869570e0d6f9d8.1531335939.git.jan.steffens@gmail.com>
References: <a2d2476ffec7d988b1a5396586869570e0d6f9d8.1531335939.git.jan.steffens@gmail.com>
From: Denis Kenzior <denkenz@gmail.com>
Date: Tue, 19 Jun 2018 10:39:50 -0500
Subject: [PATCH 4/4] mac80211: disable BHs/preemption in
 ieee80211_tx_control_port()

On pre-emption enabled kernels the following print was being seen due to
missing local_bh_disable/local_bh_enable calls.  mac80211 assumes that
pre-emption is disabled in the data path.

    BUG: using smp_processor_id() in preemptible [00000000] code: iwd/517
    caller is __ieee80211_subif_start_xmit+0x144/0x210 [mac80211]
    [...]
    Call Trace:
    dump_stack+0x5c/0x80
    check_preemption_disabled.cold.0+0x46/0x51
    __ieee80211_subif_start_xmit+0x144/0x210 [mac80211]

Fixes: 911806491425 ("mac80211: Add support for tx_control_port")
Signed-off-by: Denis Kenzior <denkenz@gmail.com>
[commit message rewrite, fixes tag]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 net/mac80211/tx.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 05a265cd573d..7404a5114597 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -4800,7 +4800,9 @@ int ieee80211_tx_control_port(struct wiphy *wiphy, struct net_device *dev,
 	skb_reset_network_header(skb);
 	skb_reset_mac_header(skb);
 
+	local_bh_disable();
 	__ieee80211_subif_start_xmit(skb, skb->dev, flags);
+	local_bh_enable();
 
 	return 0;
 }
-- 
2.18.0