[PATCH] regulator: core: Take lock before applying system load

[PATCH] regulator: core: Take lock before applying system load

[Niklas Cassel]

Take the regulator lock before applying system load.

Fixes the following lockdep splat:

[    5.583581] WARNING: CPU: 1 PID: 16 at drivers/regulator/core.c:925 drms_uA_update+0x114/0x360
[    5.588467] Modules linked in:
[    5.596833] CPU: 1 PID: 16 Comm: kworker/1:0 Not tainted 5.0.0-rc6-next-20190213-00002-g0fce66ab480f #18
[    5.599933] Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT)
[    5.609544] Workqueue: events qcom_channel_state_worker
[    5.616209] pstate: 60000005 (nZCv daif -PAN -UAO)
[    5.621152] pc : drms_uA_update+0x114/0x360
[    5.626006] lr : drms_uA_update+0x110/0x360
[    5.630084] sp : ffff0000124b3490
[    5.634242] x29: ffff0000124b3490 x28: ffff800005326e00
[    5.637735] x27: ffff0000124b35f8 x26: 000000000032bc48
[    5.643117] x25: ffff800004c7e800 x24: ffff800004c6d500
[    5.648411] x23: ffff800004c38a80 x22: 00000000000000d1
[    5.653706] x21: 00000000001ab3f0 x20: ffff800004c7e800
[    5.659001] x19: ffff0000114c3000 x18: ffffffffffffffff
[    5.664297] x17: 0000000000000000 x16: 0000000000000000
[    5.669592] x15: ffff0000114c3808 x14: 0720072007200720
[    5.674888] x13: 00000000199c9b28 x12: ffff80002bcccc40
[    5.680183] x11: ffff000012286000 x10: ffff0000114c3808
[    5.685477] x9 : 0720072007200720 x8 : ffff000010e9e808
[    5.690772] x7 : ffff0000106da568 x6 : 0000000000000000
[    5.696067] x5 : 0000000000000000 x4 : 0000000000000000
[    5.701362] x3 : 0000000000000004 x2 : 0000000000000000
[    5.706658] x1 : 0000000000000000 x0 : 0000000000000000
[    5.711952] Call trace:
[    5.717223]  drms_uA_update+0x114/0x360
[    5.719405]  regulator_register+0xb30/0x1140
[    5.723230]  devm_regulator_register+0x4c/0xa8
[    5.727745]  rpm_reg_probe+0xfc/0x1b0
[    5.731992]  platform_drv_probe+0x50/0xa0
[    5.735727]  really_probe+0x20c/0x2b8
[    5.739718]  driver_probe_device+0x58/0x100
[    5.743368]  __device_attach_driver+0x90/0xd0
[    5.747363]  bus_for_each_drv+0x64/0xc8
[    5.751870]  __device_attach+0xd8/0x138
[    5.755516]  device_initial_probe+0x10/0x18
[    5.759341]  bus_probe_device+0x98/0xa0
[    5.763502]  device_add+0x3d0/0x640
[    5.767319]  of_device_add+0x48/0x58
[    5.770793]  of_platform_device_create_pdata+0xb0/0x128
[    5.774629]  of_platform_bus_create+0x174/0x370
[    5.779569]  of_platform_populate+0x78/0xe0
[    5.784082]  qcom_smd_rpm_probe+0x80/0xa0
[    5.788245]  rpmsg_dev_probe+0x114/0x1a0
[    5.792411]  really_probe+0x20c/0x2b8
[    5.796401]  driver_probe_device+0x58/0x100
[    5.799964]  __device_attach_driver+0x90/0xd0
[    5.803960]  bus_for_each_drv+0x64/0xc8
[    5.808468]  __device_attach+0xd8/0x138
[    5.812115]  device_initial_probe+0x10/0x18
[    5.815936]  bus_probe_device+0x98/0xa0
[    5.820099]  device_add+0x3d0/0x640
[    5.823916]  device_register+0x1c/0x28
[    5.827391]  rpmsg_register_device+0x4c/0x90
[    5.831216]  qcom_channel_state_worker+0x170/0x298
[    5.835651]  process_one_work+0x294/0x6e8
[    5.840241]  worker_thread+0x40/0x450
[    5.844318]  kthread+0x11c/0x120
[    5.847961]  ret_from_fork+0x10/0x18
[    5.851260] irq event stamp: 9090
[    5.854820] hardirqs last  enabled at (9089): [<ffff000010160798>] console_unlock+0x3e0/0x5b0
[    5.858086] hardirqs last disabled at (9090): [<ffff0000100817cc>] do_debug_exception+0x104/0x140
[    5.866596] softirqs last  enabled at (9086): [<ffff000010082024>] __do_softirq+0x474/0x574
[    5.875446] softirqs last disabled at (9079): [<ffff0000100f2254>] irq_exit+0x13c/0x148
[    5.883598] ---[ end trace 6984ef7f081afa21 ]---

Fixes: fa94e48e13a1 ("regulator: core: Apply system load even if no consumer loads")
Signed-off-by: Niklas Cassel <niklas.cassel@linaro.org>
---
Hello Mark,

I'm not that familiar with regulator core,
please verify that I'm using the correct
locking function here.


 drivers/regulator/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 224f62d27ad7..7ed134afb316 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1347,7 +1347,9 @@ static int set_machine_constraints(struct regulator_dev *rdev,
 		 * We'll only apply the initial system load if an
 		 * initial mode wasn't specified.
 		 */
+		regulator_lock(rdev);
 		drms_uA_update(rdev);
+		regulator_unlock(rdev);
 	}
 
 	if ((rdev->constraints->ramp_delay || rdev->constraints->ramp_disable)
-- 
2.20.1

Re: [PATCH] regulator: core: Take lock before applying system load

[Mark Brown]

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On Fri, Feb 15, 2019 at 11:55:33AM +0100, Niklas Cassel wrote:
> Take the regulator lock before applying system load.
> 
> Fixes the following lockdep splat:
> 
> [    5.583581] WARNING: CPU: 1 PID: 16 at drivers/regulator/core.c:925 drms_uA_update+0x114/0x360
> [    5.588467] Modules linked in:
> [    5.596833] CPU: 1 PID: 16 Comm: kworker/1:0 Not tainted 5.0.0-rc6-next-20190213-00002-g0fce66ab480f #18

Please think hard before including complete backtraces in upstream
reports, they are very large and contain almost no useful information
relative to their size so often obscure the relevant content in your
message. If part of the backtrace is usefully illustrative then it's
usually better to pull out the relevant sections.

>  		 * We'll only apply the initial system load if an
>  		 * initial mode wasn't specified.
>  		 */
> +		regulator_lock(rdev);
>  		drms_uA_update(rdev);
> +		regulator_unlock(rdev);

This is correct in that it will shut up the warning but we're not
supposed to need locks at this point as the regulator is in the process
of being registered so there should be no possibility of concurrent
access.  Since I can't see a sensible way to conditionally assert that
the lock is held we're probably better off just removing the annotation
since it's no longer valid.

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