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SubjectRe: [PATCH v4 03/13] extcon: arizona: Fix various races on driver unbind
On Sat, Jan 23, 2021 at 01:13:03PM +0100, Hans de Goede wrote:
> We must free/disable all interrupts and cancel all pending works
> before doing further cleanup.
>
> Before this commit arizona_extcon_remove() was doing several
> register writes to shut things down before disabling the IRQs
> and it was cancelling only 1 of the 3 different works used.
>
> Move all the register-writes shutting things down to after
> the disabling of the IRQs and add the 2 missing
> cancel_delayed_work_sync() calls.
>
> This fixes various possible races on driver unbind. One of which
> would always trigger on devices using the mic-clamp feature for
> jack detection. The ARIZONA_MICD_CLAMP_MODE_MASK update was
> done before disabling the IRQs, causing:
> 1. arizona_jackdet() to run
> 2. detect a jack being inserted (clamp disabled means jack inserted)
> 3. call arizona_start_mic() which:
> 3.1 Enables the MICVDD regulator
> 3.2 takes a pm_runtime_reference
>
> And this was all happening after the ARIZONA_MICD_ENA bit clearing,
> which would undo 3.1 and 3.2 because the ARIZONA_MICD_CLAMP_MODE_MASK
> update was being done after the ARIZONA_MICD_ENA bit clearing.
>
> So this means that arizona_extcon_remove() would exit with
> 1. MICVDD enabled and 2. The pm_runtime_reference being unbalanced.
>
> MICVDD still being enabled caused the following oops when the
> regulator is released by the devm framework:
>
> [ 2850.745757] ------------[ cut here ]------------
> [ 2850.745827] WARNING: CPU: 2 PID: 2098 at drivers/regulator/core.c:2123 _regulator_put.part.0+0x19f/0x1b0
> [ 2850.745835] Modules linked in: extcon_arizona ...
> ...
> [ 2850.746909] Call Trace:
> [ 2850.746932] regulator_put+0x2d/0x40
> [ 2850.746946] release_nodes+0x22a/0x260
> [ 2850.746984] __device_release_driver+0x190/0x240
> [ 2850.747002] driver_detach+0xd4/0x120
> ...
> [ 2850.747337] ---[ end trace f455dfd7abd9781f ]---
>
> Note this oops is just one of various theoretically possible races caused
> by the wrong ordering inside arizona_extcon_remove(), this fixes the
> ordering fixing all possible races, including the reported oops.
>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---

Tested-by: Charles Keepax <ckeepax@opensource.cirrus.com>

Thanks,
Charles

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