linux-kernel - [PATCH v2 3/3] pmbus

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Date:   Tue, 25 Jul 2023 14:54:27 +0200
From:   Naresh Solanki <naresh.solanki@...ements.com>
To:     Guenter Roeck <linux@...ck-us.net>, linux-hwmon@...r.kernel.org,
        Jean Delvare <jdelvare@...e.com>
Cc:     Patrick Rudolph <patrick.rudolph@...ements.com>,
        Naresh Solanki <Naresh.Solanki@...ements.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/3] pmbus_core: Fix Deadlock

From: Patrick Rudolph <patrick.rudolph@...ements.com>

pmbus_regulator_get_error_flags() will also acquire the update_lock,
thus unlock the mutex before trying to lock it again from within
the same thread.

Fixes a deadlock when trying to read the regulator status.

Signed-off-by: Patrick Rudolph <patrick.rudolph@...ements.com>
Signed-off-by: Naresh Solanki <Naresh.Solanki@...ements.com>
---
 drivers/hwmon/pmbus/pmbus_core.c | 30 ++++++++++--------------------
 1 file changed, 10 insertions(+), 20 deletions(-)

diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index 30aeb59062a5..42f4250c53ed 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -2949,37 +2949,27 @@ static int pmbus_regulator_get_status(struct regulator_dev *rdev)
 
 	mutex_lock(&data->update_lock);
 	status = pmbus_get_status(client, page, PMBUS_STATUS_WORD);
-	if (status < 0) {
-		ret = status;
-		goto unlock;
-	}
+	mutex_unlock(&data->update_lock);
+	if (status < 0)
+		return status;
 
-	if (status & PB_STATUS_OFF) {
-		ret = REGULATOR_STATUS_OFF;
-		goto unlock;
-	}
+	if (status & PB_STATUS_OFF)
+		return REGULATOR_STATUS_OFF;
 
 	/* If regulator is ON & reports power good then return ON */
-	if (!(status & PB_STATUS_POWER_GOOD_N)) {
-		ret = REGULATOR_STATUS_ON;
-		goto unlock;
-	}
+	if (!(status & PB_STATUS_POWER_GOOD_N))
+		return REGULATOR_STATUS_ON;
 
 	ret = pmbus_regulator_get_error_flags(rdev, &status);
 	if (ret)
-		goto unlock;
+		return ret;
 
 	if (status & (REGULATOR_ERROR_UNDER_VOLTAGE | REGULATOR_ERROR_OVER_CURRENT |
 	   REGULATOR_ERROR_REGULATION_OUT | REGULATOR_ERROR_FAIL | REGULATOR_ERROR_OVER_TEMP)) {
-		ret = REGULATOR_STATUS_ERROR;
-		goto unlock;
+		return REGULATOR_STATUS_ERROR;
 	}
 
-	ret = REGULATOR_STATUS_UNDEFINED;
-
-unlock:
-	mutex_unlock(&data->update_lock);
-	return ret;
+	return REGULATOR_STATUS_UNDEFINED;
 }
 
 static int pmbus_regulator_get_low_margin(struct i2c_client *client, int page)
-- 
2.41.0