linux-kernel - [PATCH] regulator: core: fix deadlock on regulator enable

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Message-Id: <20221215104646.19818-1-johan+linaro@kernel.org>
Date:   Thu, 15 Dec 2022 11:46:46 +0100
From:   Johan Hovold <johan+linaro@...nel.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Maciej Purski <m.purski@...sung.com>,
        Dmitry Osipenko <digetx@...il.com>,
        linux-kernel@...r.kernel.org,
        Johan Hovold <johan+linaro@...nel.org>, stable@...r.kernel.org
Subject: [PATCH] regulator: core: fix deadlock on regulator enable

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@...r.kernel.org      # 5.0
Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
---
 drivers/regulator/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 729c45393803..ae69e493913d 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1002,7 +1002,7 @@ static int drms_uA_update(struct regulator_dev *rdev)
 		/* 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;
 
-- 
2.37.4