From:   Lorenzo Bianconi <lorenzo@kernel.org>
To:     nbd@nbd.name
Cc:     lorenzo.bianconi@redhat.com, linux-wireless@vger.kernel.org,
        sean.wang@mediatek.com, deren.wu@mediatek.com
Subject: [PATCH 1/2] mt76: mt7921: fix a leftover race in runtime-pm
Date:   Thu, 30 Dec 2021 21:47:05 +0100
Message-Id: <65e65daddbcec420392befa3b4f9a6aaaea21315.1640897147.git.lorenzo@kernel.org>
In-Reply-To: <cover.1640897147.git.lorenzo@kernel.org>
References: <cover.1640897147.git.lorenzo@kernel.org>
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Fix a possible race in mt7921_pm_power_save_work() if rx/tx napi
schedules ps_work and we are currently accessing device register
on a different cpu.

Fixes: 1d8efc741df8 ("mt76: mt7921: introduce Runtime PM support")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 drivers/net/wireless/mediatek/mt76/mt7921/mac.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/mac.c b/drivers/net/wireless/mediatek/mt76/mt7921/mac.c
index defef3496246..0744f6e42ba3 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7921/mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7921/mac.c
@@ -1553,6 +1553,14 @@ void mt7921_pm_power_save_work(struct work_struct *work)
 	    dev->fw_assert)
 		goto out;
 
+	if (mutex_is_locked(&dev->mt76.mutex))
+		/* if mt76 mutex is held we should not put the device
+		 * to sleep since we are currently accessing device
+		 * register map. We need to wait for the next power_save
+		 * trigger.
+		 */
+		goto out;
+
 	if (time_is_after_jiffies(dev->pm.last_activity + delta)) {
 		delta = dev->pm.last_activity + delta - jiffies;
 		goto out;
-- 
2.33.1