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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Lorenzo Bianconi <lorenzo@kernel.org>,
        Felix Fietkau <nbd@nbd.name>, Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.17 0499/1126] mt76: mt7615: fix a leftover race in runtime-pm
Date:   Tue,  5 Apr 2022 09:20:46 +0200
Message-Id: <20220405070422.273651178@linuxfoundation.org>
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From: Lorenzo Bianconi <lorenzo@kernel.org>

[ Upstream commit 42ce8d3b623162f3248db50a38359f294e6b06fd ]

Fix a possible race in mt7615_pm_power_save_work() if rx/tx napi
schedules ps_work and we are currently accessing device register
on a different cpu.

Fixes: db928f1ab9789 ("mt76: mt7663: rely on mt76_connac_pm_ref/mt76_connac_pm_unref in tx/rx napi")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/wireless/mediatek/mt76/mt7615/mac.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7615/mac.c b/drivers/net/wireless/mediatek/mt76/mt7615/mac.c
index ec25e5a95d44..6d0ff5af8fec 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7615/mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7615/mac.c
@@ -2103,6 +2103,14 @@ void mt7615_pm_power_save_work(struct work_struct *work)
 	    test_bit(MT76_HW_SCHED_SCANNING, &dev->mphy.state))
 		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;
-- 
2.34.1