Date:   Thu, 24 Nov 2016 15:45:52 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        linaro-kernel <linaro-kernel@...ts.linaro.org>,
        ckeepax@...nsource.wolfsonmicro.com,
        patches@...nsource.wolfsonmicro.com,
        Jaehoon Chung <jh80.chung@...sung.com>
Subject: Re: [PATCH V4] mfd: wm8994-core: Don't use managed regulator bulk get API

+ Jaehoon

On 10 November 2016 at 09:39, Lee Jones <lee.jones@...aro.org> wrote:
> On Thu, 27 Oct 2016, Viresh Kumar wrote:
>
>> The kernel WARNs and then crashes today if wm8994_device_init() fails
>> after calling devm_regulator_bulk_get().
>>
>> That happens because there are multiple devices involved here and the
>> order in which managed resources are freed isn't correct.
>>
>> The regulators are added as children of wm8994->dev.  Whereas,
>> devm_regulator_bulk_get() receives wm8994->dev as the device, though it
>> gets the same regulators which were added as children of wm8994->dev
>> earlier.
>>
>> During failures, the children are removed first and the core eventually
>> calls regulator_unregister() for them. As regulator_put() was never done
>> for them (opposite of devm_regulator_bulk_get()), the kernel WARNs at
>>
>>       WARN_ON(rdev->open_count);
>>
>> And eventually it crashes from debugfs_remove_recursive().
>
> Applied, thanks.

Lee, did you intend to send this a fix for 4.9 rc? I would be nice as
kernelci are reporting this issue (assuming it's the same).

https://kernelci.org/boot/all/job/ulfh/kernel/v4.9-rc5-78-g52eb5d4531e4/

Kind regards
Uffe

>
>> --------x------------------x----------------
>>
>>  wm8994 3-001a: Device is not a WM8994, ID is 0
>>  ------------[ cut here ]------------
>>  WARNING: CPU: 0 PID: 1 at /mnt/ssd/all/work/repos/devel/linux/drivers/regulator/core.c:4072 regulator_unregister+0xc8/0xd0
>>  Modules linked in:
>>  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.8.0-rc6-00154-g54fe84cbd50b #41
>>  Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
>>  [<c010e24c>] (unwind_backtrace) from [<c010af38>] (show_stack+0x10/0x14)
>>  [<c010af38>] (show_stack) from [<c032a1c4>] (dump_stack+0x88/0x9c)
>>  [<c032a1c4>] (dump_stack) from [<c011a98c>] (__warn+0xe8/0x100)
>>  [<c011a98c>] (__warn) from [<c011aa54>] (warn_slowpath_null+0x20/0x28)
>>  [<c011aa54>] (warn_slowpath_null) from [<c0384a0c>] (regulator_unregister+0xc8/0xd0)
>>  [<c0384a0c>] (regulator_unregister) from [<c0406434>] (release_nodes+0x16c/0x1dc)
>>  [<c0406434>] (release_nodes) from [<c04039c4>] (__device_release_driver+0x8c/0x110)
>>  [<c04039c4>] (__device_release_driver) from [<c0403a64>] (device_release_driver+0x1c/0x28)
>>  [<c0403a64>] (device_release_driver) from [<c0402b24>] (bus_remove_device+0xd8/0x104)
>>  [<c0402b24>] (bus_remove_device) from [<c03ffcd8>] (device_del+0x10c/0x218)
>>  [<c03ffcd8>] (device_del) from [<c0404e4c>] (platform_device_del+0x1c/0x88)
>>  [<c0404e4c>] (platform_device_del) from [<c0404ec4>] (platform_device_unregister+0xc/0x20)
>>  [<c0404ec4>] (platform_device_unregister) from [<c0428bc0>] (mfd_remove_devices_fn+0x5c/0x64)
>>  [<c0428bc0>] (mfd_remove_devices_fn) from [<c03ff9d8>] (device_for_each_child_reverse+0x4c/0x78)
>>  [<c03ff9d8>] (device_for_each_child_reverse) from [<c04288c4>] (mfd_remove_devices+0x20/0x30)
>>  [<c04288c4>] (mfd_remove_devices) from [<c042758c>] (wm8994_device_init+0x2ac/0x7f0)
>>  [<c042758c>] (wm8994_device_init) from [<c04f14a8>] (i2c_device_probe+0x178/0x1fc)
>>  [<c04f14a8>] (i2c_device_probe) from [<c04036fc>] (driver_probe_device+0x214/0x2c0)
>>  [<c04036fc>] (driver_probe_device) from [<c0403854>] (__driver_attach+0xac/0xb0)
>>  [<c0403854>] (__driver_attach) from [<c0401a74>] (bus_for_each_dev+0x68/0x9c)
>>  [<c0401a74>] (bus_for_each_dev) from [<c0402cf0>] (bus_add_driver+0x1a0/0x218)
>>  [<c0402cf0>] (bus_add_driver) from [<c040406c>] (driver_register+0x78/0xf8)
>>  [<c040406c>] (driver_register) from [<c04f20a0>] (i2c_register_driver+0x34/0x84)
>>  [<c04f20a0>] (i2c_register_driver) from [<c01017d0>] (do_one_initcall+0x40/0x170)
>>  [<c01017d0>] (do_one_initcall) from [<c0a00dbc>] (kernel_init_freeable+0x15c/0x1fc)
>>  [<c0a00dbc>] (kernel_init_freeable) from [<c06e07b0>] (kernel_init+0x8/0x114)
>>  [<c06e07b0>] (kernel_init) from [<c0107978>] (ret_from_fork+0x14/0x3c)
>>  ---[ end trace 0919d3d0bc998260 ]---
>>
>>  [snip..]
>>
>>  Unable to handle kernel NULL pointer dereference at virtual address 00000078
>>  pgd = c0004000
>>  [00000078] *pgd=00000000
>>  Internal error: Oops: 5 [#1] PREEMPT SMP ARM
>>  Modules linked in:
>>  CPU: 0 PID: 1 Comm: swapper/0 Tainted: G        W       4.8.0-rc6-00154-g54fe84cbd50b #41
>>  Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
>>  task: ee874000 task.stack: ee878000
>>  PC is at down_write+0x14/0x54
>>  LR is at debugfs_remove_recursive+0x30/0x150
>>
>>  [snip..]
>>
>>  [<c06e489c>] (down_write) from [<c02e9954>] (debugfs_remove_recursive+0x30/0x150)
>>  [<c02e9954>] (debugfs_remove_recursive) from [<c0382b78>] (_regulator_put+0x24/0xac)
>>  [<c0382b78>] (_regulator_put) from [<c0382c1c>] (regulator_put+0x1c/0x2c)
>>  [<c0382c1c>] (regulator_put) from [<c0406434>] (release_nodes+0x16c/0x1dc)
>>  [<c0406434>] (release_nodes) from [<c04035d4>] (driver_probe_device+0xec/0x2c0)
>>  [<c04035d4>] (driver_probe_device) from [<c0403854>] (__driver_attach+0xac/0xb0)
>>  [<c0403854>] (__driver_attach) from [<c0401a74>] (bus_for_each_dev+0x68/0x9c)
>>  [<c0401a74>] (bus_for_each_dev) from [<c0402cf0>] (bus_add_driver+0x1a0/0x218)
>>  [<c0402cf0>] (bus_add_driver) from [<c040406c>] (driver_register+0x78/0xf8)
>>  [<c040406c>] (driver_register) from [<c04f20a0>] (i2c_register_driver+0x34/0x84)
>>  [<c04f20a0>] (i2c_register_driver) from [<c01017d0>] (do_one_initcall+0x40/0x170)
>>  [<c01017d0>] (do_one_initcall) from [<c0a00dbc>] (kernel_init_freeable+0x15c/0x1fc)
>>  [<c0a00dbc>] (kernel_init_freeable) from [<c06e07b0>] (kernel_init+0x8/0x114)
>>  [<c06e07b0>] (kernel_init) from [<c0107978>] (ret_from_fork+0x14/0x3c)
>>  Code: e1a04000 f590f000 e3a03001 e34f3fff (e1902f9f)
>>  ---[ end trace 0919d3d0bc998262 ]---
>>
>> --------x------------------x----------------
>>
>> Fix the kernel warnings and crashes by using regulator_bulk_get()
>> instead of devm_regulator_bulk_get() and explicitly freeing the supplies
>> in exit paths.
>>
>> Tested on Exynos 5250, dual core ARM A15 machine.
>>
>> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
>> Acked-by: Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
>> ---
>> V3->V4:
>> - Send the right version of the patch, sent the older one by mistake earlier.
>>
>> V2->V3:
>> - Fixed a rebase conflict
>> - sending only one patch with Charles Ack
>>
>> V1->V2:
>> - Use regulator_bulk_free() instead of open coding it.
>> - Shorter backtrace
>> - Reworded the last paragraph to make it more clear
>> - Added a comment in code
>>
>>  drivers/mfd/wm8994-core.c | 14 +++++++++++---
>>  1 file changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/mfd/wm8994-core.c b/drivers/mfd/wm8994-core.c
>> index 95e6bc55adbb..953d0790ffd5 100644
>> --- a/drivers/mfd/wm8994-core.c
>> +++ b/drivers/mfd/wm8994-core.c
>> @@ -393,8 +393,13 @@ static int wm8994_device_init(struct wm8994 *wm8994, int irq)
>>               BUG();
>>               goto err;
>>       }
>> -
>> -     ret = devm_regulator_bulk_get(wm8994->dev, wm8994->num_supplies,
>> +
>> +     /*
>> +      * Can't use devres helper here as some of the supplies are provided by
>> +      * wm8994->dev's children (regulators) and those regulators are
>> +      * unregistered by the devres core before the supplies are freed.
>> +      */
>> +     ret = regulator_bulk_get(wm8994->dev, wm8994->num_supplies,
>>                                wm8994->supplies);
>>       if (ret != 0) {
>>               dev_err(wm8994->dev, "Failed to get supplies: %d\n", ret);
>> @@ -404,7 +409,7 @@ static int wm8994_device_init(struct wm8994 *wm8994, int irq)
>>       ret = regulator_bulk_enable(wm8994->num_supplies, wm8994->supplies);
>>       if (ret != 0) {
>>               dev_err(wm8994->dev, "Failed to enable supplies: %d\n", ret);
>> -             goto err;
>> +             goto err_regulator_free;
>>       }
>>
>>       ret = wm8994_reg_read(wm8994, WM8994_SOFTWARE_RESET);
>> @@ -595,6 +600,8 @@ static int wm8994_device_init(struct wm8994 *wm8994, int irq)
>>  err_enable:
>>       regulator_bulk_disable(wm8994->num_supplies,
>>                              wm8994->supplies);
>> +err_regulator_free:
>> +     regulator_bulk_free(wm8994->num_supplies, wm8994->supplies);
>>  err:
>>       mfd_remove_devices(wm8994->dev);
>>       return ret;
>> @@ -605,6 +612,7 @@ static void wm8994_device_exit(struct wm8994 *wm8994)
>>       pm_runtime_disable(wm8994->dev);
>>       wm8994_irq_exit(wm8994);
>>       regulator_bulk_disable(wm8994->num_supplies, wm8994->supplies);
>> +     regulator_bulk_free(wm8994->num_supplies, wm8994->supplies);
>>       mfd_remove_devices(wm8994->dev);
>>  }
>>
>
> --
> Lee Jones
> Linaro STMicroelectronics Landing Team Lead
> Linaro.org │ Open source software for ARM SoCs
> Follow Linaro: Facebook | Twitter | Blog
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