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@kernel.org>
Link: https://lore.kernel.org/r/20221214131617.2447-5-johan+linaro@kernel.org
Signed-off-by: Daniel Lezcano <daniel.lezcano@kernel.org>

diff --git a/drivers/thermal/qcom/qcom-spmi-temp-alarm.c b/drivers/thermal/qcom/qcom-spmi-temp-alarm.c
index bfaec74f13b24f4f84c7ae730b89d7436a3e7f3c..e2429676d0d26ae5e3371b45551fd20c2ff09663 100644 (file)
--- 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;