linux-kernel - [PATCH 4/4] thermal/drivers/qcom: fix lock inversion

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Date:   Wed, 14 Dec 2022 14:16:17 +0100
From:   Johan Hovold <johan+linaro@...nel.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Amit Kucheria <amitk@...nel.org>,
        Thara Gopinath <thara.gopinath@...il.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        linux-pm@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org,
        Johan Hovold <johan+linaro@...nel.org>
Subject: [PATCH 4/4] thermal/drivers/qcom: fix lock inversion

The thermal-zone-device lock is held by core when setting trip points
and the driver takes its chip lock in the corresponding callback.

Fetching the thermal trip points using thermal_zone_get_trip() also
involves taking the thermal-zone-device lock, which means that the chip
lock can not be held when doing so.

Drop the chip lock temporarily during probe to avoid the lock inversion
that was detected by lockdep:

  ======================================================
  WARNING: possible circular locking dependency detected
  6.1.0-next-20221213 #122 Not tainted
  ------------------------------------------------------
  systemd-udevd/264 is trying to acquire lock:
  ffff741e444a0920 (&chip->lock){+.+.}-{3:3}, at: qpnp_tm_get_temp+0xb4/0x1b0 [qcom_spmi_temp_alarm]

  but task is already holding lock:
  ffff741e44341618 (&tz->lock){+.+.}-{3:3}, at: thermal_zone_device_update+0x2c/0x70

  which lock already depends on the new lock.

Fixes: 78c3e2429be8 ("thermal/drivers/qcom: Use generic thermal_zone_get_trip() function")
Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
---
 drivers/thermal/qcom/qcom-spmi-temp-alarm.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/thermal/qcom/qcom-spmi-temp-alarm.c b/drivers/thermal/qcom/qcom-spmi-temp-alarm.c
index bfaec74f13b2..e2429676d0d2 100644
--- a/drivers/thermal/qcom/qcom-spmi-temp-alarm.c
+++ b/drivers/thermal/qcom/qcom-spmi-temp-alarm.c
@@ -348,7 +348,12 @@ static int qpnp_tm_init(struct qpnp_tm_chip *chip)
 	if (stage)
 		chip->temp = qpnp_tm_decode_temp(chip, stage);
 
+	mutex_unlock(&chip->lock);
+
 	crit_temp = qpnp_tm_get_critical_trip_temp(chip);
+
+	mutex_lock(&chip->lock);
+
 	ret = qpnp_tm_update_critical_trip_temp(chip, crit_temp);
 	if (ret < 0)
 		goto out;
-- 
2.37.4