[PATCH 5.15 721/731] regulator: core: fix deadlock on regulator enable

Greg Kroah-Hartman
2022-12-28T16:04:00Z

From: Johan Hovold <johan+linaro@kernel.org>

commit cb3543cff90a4448ed560ac86c98033ad5fecda9 upstream.

When updating the operating mode as part of regulator enable, the caller
has already locked the regulator tree and drms_uA_update() must not try
to do the same in order not to trigger a deadlock.

The lock inversion is reported by lockdep as:

======================================================
WARNING: possible circular locking dependency detected
6.1.0-next-20221215 #142 Not tainted
------------------------------------------------------
udevd/154 is trying to acquire lock:
ffffc11f123d7e50 (regulator_list_mutex){+.+.}-{3:3}, at: regulator_lock_dependent+0x54/0x280

but task is already holding lock:
ffff80000e4c36e8 (regulator_ww_class_acquire){+.+.}-{0:0}, at: regulator_enable+0x34/0x80

which lock already depends on the new lock.

...

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(regulator_ww_class_acquire);
lock(regulator_list_mutex);
lock(regulator_ww_class_acquire);
lock(regulator_list_mutex);

*** DEADLOCK ***

just before probe of a Qualcomm UFS controller (occasionally) deadlocks
when enabling one of its regulators.

Fixes: 9243a195be7a ("regulator: core: Change voltage setting path")
Fixes: f8702f9e4aa7 ("regulator: core: Use ww_mutex for regulators locking")
Cc: stable@vger.kernel.org # 5.0
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20221215104646.19818-1-johan+linaro@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/regulator/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -962,7 +962,7 @@ static int drms_uA_update(struct regulat
/* get input voltage */
input_uV = 0;
if (rdev->supply)
- input_uV = regulator_get_voltage(rdev->supply);
+ input_uV = regulator_get_voltage_rdev(rdev->supply->rdev);
if (input_uV <= 0)
input_uV = rdev->constraints->input_uV;
if (input_uV <= 0) {