Received-SPF: pass (google.com: domain of linux-wireless-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Shuah Khan <skhan@linuxfoundation.org>
To:     peterz@infradead.org, mingo@redhat.com, will@kernel.org,
        kvalo@codeaurora.org, davem@davemloft.net, kuba@kernel.org
Cc:     Shuah Khan <skhan@linuxfoundation.org>, ath10k@lists.infradead.org,
        linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH v2 3/3] ath10k: detect conf_mutex held ath10k_drain_tx() calls
Date:   Fri, 26 Feb 2021 10:52:15 -0700
Message-Id: <38eef822d97917db50068eb65eb71ae3b83eb43e.1614355914.git.skhan@linuxfoundation.org>
In-Reply-To: <cover.1614355914.git.skhan@linuxfoundation.org>
References: <cover.1614355914.git.skhan@linuxfoundation.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

ath10k_drain_tx() must not be called with conf_mutex held as workers can
use that also. Add call to lockdep_assert_not_held() on conf_mutex to
detect if conf_mutex is held by the caller.

The idea for this patch stemmed from coming across the comment block
above the ath10k_drain_tx() while reviewing the conf_mutex holds during
to debug the conf_mutex lock assert in ath10k_debug_fw_stats_request().

Adding detection to assert on conf_mutex hold will help detect incorrect
usages that could lead to locking problems when async worker routines try
to call this routine.

Link: https://lore.kernel.org/lkml/37a29c383bff2fb1605241ee6c7c9be3784fb3c6.1613171185.git.skhan@linuxfoundation.org/
Link: https://lore.kernel.org/linux-wireless/871rdmu9z9.fsf@codeaurora.org/
Acked-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
 drivers/net/wireless/ath/ath10k/mac.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
index 7d98250380ec..a595ff4f0843 100644
--- a/drivers/net/wireless/ath/ath10k/mac.c
+++ b/drivers/net/wireless/ath/ath10k/mac.c
@@ -4567,6 +4567,8 @@ static void ath10k_mac_op_wake_tx_queue(struct ieee80211_hw *hw,
 /* Must not be called with conf_mutex held as workers can use that also. */
 void ath10k_drain_tx(struct ath10k *ar)
 {
+	lockdep_assert_not_held(&ar->conf_mutex);
+
 	/* make sure rcu-protected mac80211 tx path itself is drained */
 	synchronize_net();
 
-- 
2.27.0