linux-kernel - [PATCH 5.17 0498/1126] mt76: mt7921: fix a leftover race in runtime-pm

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Date:   Tue,  5 Apr 2022 09:20:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Lorenzo Bianconi <lorenzo@...nel.org>,
        Felix Fietkau <nbd@....name>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.17 0498/1126] mt76: mt7921: fix a leftover race in runtime-pm

From: Lorenzo Bianconi <lorenzo@...nel.org>

[ Upstream commit 591cdccebdd4d02eb46d400dea911136400cc567 ]

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@...nel.org>
Signed-off-by: Felix Fietkau <nbd@....name>
Signed-off-by: Sasha Levin <sashal@...nel.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 ec10f95a4649..3e83a0c33143 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7921/mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7921/mac.c
@@ -1551,6 +1551,14 @@ void mt7921_pm_power_save_work(struct work_struct *work)
 	    test_bit(MT76_HW_SCHED_SCANNING, &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