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regulator: core: fix deadlock on regulator enable 

commit cb3543cff9 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: 9243a195be ("regulator: core: Change voltage setting path")
Fixes: f8702f9e4a ("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>
This commit is contained in:
Johan Hovold 2022-12-15 11:46:46 +01:00 committed by Greg Kroah-Hartman
parent d8c1111add
commit 129b7cefa9
1 changed files with 1 additions and 1 deletions
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2
drivers/regulator/core.c
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@ -987,7 +987,7 @@ 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;
if (input_uV <= 0) {