Hi Krzysztof,
On Mon, Jan 05, 2015 at 04:47:43PM +0100, Krzysztof Kozlowski wrote:
> This is RFC, please don't apply yet but let me know if this approach
> is OK.
I just reviewed the patchset. It looks fine to me.
> TLDR
> ====
> Patchset tries to fix following race scenario:
>
> Thread 1: charger manager, CONSUMER
> Thread 2: power supply driver, PROVIDER
>
> THREAD 1 (charger manager) THREAD 2 (power supply driver)
> ========================== ==============================
> psy = power_supply_get_by_name()
> Driver unbind, .remove
> power_supply_unregister()
> Device fully removed
> psy->get_property()
>
> To properly fix the race the patchset:
> 1. Adds power_supply_get_property()-like API for safe access by consumer.
> 2. Moves ownership of power_supply structure from driver (provider) to
> power supply core.
> 3. Adds power_supply_put() which will reclaim memory.
Looks fine to me, thanks for doing this :)
> Description
> ===========
> This is a little different than my previous approaches [1][2] for fixing
> usage of power supply by some consumer, if driver implementing it is
> unbound.
>
> The patchset is quite big and touches power supply API so a lot of
> changes in drivers are needed. These changes *are not finished yet*.
> I've done them only for:
> - bq24190_charger.c
> - charger-manager.c
> - max14577_charger.c
> - max17040_battery.c
> - max17042_battery.c
> - sbs-battery.c
> - tps65090-charger.c
> So allyesconfig won't build.
>
> If this approach is OK, I'll prepare full patchset changing all the
> drivers.
Please do :)
> My previous approach [1][2] limited the race but did not close it.
> Still the consumer of power supply by calling power_supply_get_propert(psy...)
> may reference invalid memory because the producer freed it.
>
> Actually, because struct power_supply is exposed to consumers, the
> core should be the owner of it. This is accomplished in patch 11/19
> ("power_supply: Change ownership from driver to core").
>
> What the patchset does in steps
> ===============================
> 1. Some preparation steps are necessary - patch 1 and 2. The driver
> implementing power supply won't be able to fill structure before
> calling power_supply_register(). So 'power_supply_config'
> is introduced in patch 2 ("power_supply: Move run-time configuration
> to separate structure"). Unfortunately this touches all drivers.
$ grep -l power_supply_register **/*.c | grep -v mod.c | grep -v drivers/power
drivers/acpi/ac.c
drivers/acpi/battery.c
drivers/acpi/sbs.c
drivers/hid/hid-input.c
drivers/hid/hid-sony.c
drivers/hid/hid-wiimote-modules.c
drivers/hid/wacom_sys.c
drivers/platform/x86/compal-laptop.c
drivers/staging/nvec/nvec_power.c
Please make sure to CC the respective maintainers for the patchset
(e.g. current patch 14 and 15 should have CC'd x86 maintainers), so
that they can Acknowledge the patchset.
> 2. Safe API wrappers (and usage counter) are added (power_supply_*()).
> 3. Patch 11: ownership of 'struct power_supply' is moved from driver
> to the core.
> 4. power_supply_put() is added which reclaims resources.
Looks fine to me.
> The patchset is rebased on next-20141226. It should be pulled at once.
> Bisectability is preserved.
Fine with me, but I need acks from all involved maintainers. So for the
patchset:
Reviewed-By: Sebastian Reichel <sre@xxxxxxxxxx>
-- Sebastian
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