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From:   Fabio Estevam <festevam@denx.de>
To:     kvalo@codeaurora.org
Cc:     kuba@kernel.org, ath10k@lists.infradead.org,
        linux-wireless@vger.kernel.org, paulmck@kernel.org, marex@denx.de,
        wgong@codeaurora.org, alagusankar@silex-india.com,
        erik.stromdahl@gmail.com, Fabio Estevam <festevam@denx.de>
Subject: [PATCH] ath10k: sdio: Add missing BH locking around napi_schdule()
Date:   Tue, 24 Aug 2021 11:43:39 -0300
Message-Id: <20210824144339.2796122-1-festevam@denx.de>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

On a i.MX-based board with a QCA9377 Wifi chip, the following errors
are seen after launching the 'hostapd' application:

hostapd /etc/wifi.conf
Configuration file: /etc/wifi.conf
wlan0: interface state UNINITIALIZED->COUNTRY_UPDATE
NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!
Using interface wlan0 with hwaddr 00:1f:7b:31:04:a0 and ssid "thessid"
IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
wlan0: interface state COUNTRY_UPDATE->ENABLED
wlan0: AP-ENABLED
NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!
NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!
NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!
NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!
...

Fix this problem by adding the BH locking around napi-schedule(),
in the same way it was done in commit e63052a5dd3c ("mlx5e: add
add missing BH locking around napi_schdule()").

Its commit log provides the following explanation:

"It's not correct to call napi_schedule() in pure process
context. Because we use __raise_softirq_irqoff() we require
callers to be in a context which will eventually lead to
softirq handling (hardirq, bh disabled, etc.).
    
With code as is users will see:
    
NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!
"

Fixes: cfee8793a74d ("ath10k: enable napi on RX path for sdio")
Signed-off-by: Fabio Estevam <festevam@denx.de>
---
 drivers/net/wireless/ath/ath10k/sdio.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/ath10k/sdio.c b/drivers/net/wireless/ath/ath10k/sdio.c
index b746052737e0..eb705214f3f0 100644
--- a/drivers/net/wireless/ath/ath10k/sdio.c
+++ b/drivers/net/wireless/ath/ath10k/sdio.c
@@ -1363,8 +1363,11 @@ static void ath10k_rx_indication_async_work(struct work_struct *work)
 		ep->ep_ops.ep_rx_complete(ar, skb);
 	}
 
-	if (test_bit(ATH10K_FLAG_CORE_REGISTERED, &ar->dev_flags))
+	if (test_bit(ATH10K_FLAG_CORE_REGISTERED, &ar->dev_flags)) {
+		local_bh_disable();
 		napi_schedule(&ar->napi);
+		local_bh_enable();
+	}
 }
 
 static int ath10k_sdio_read_rtc_state(struct ath10k_sdio *ar_sdio, unsigned char *state)
-- 
2.25.1