Messages in this thread Patch in this message | | | From | Krzysztof Kozlowski <> | Subject | [PATCH v2 1/8] power_supply: Add API for safe access of power supply function attrs | Date | Thu, 16 Oct 2014 09:32:50 +0200 |
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Add simple wrappers for accessing power supply's function attributes: - get_property -> power_supply_get_property - set_property -> power_supply_set_property - property_is_writeable -> power_supply_property_is_writeable - external_power_changed -> power_supply_external_power_changed - set_charged -> power_supply_set_charged
This API adds a safe way of accessing a power supply from another driver. Particularly it solves invalid memory references (and lockup) in following race condition scenario:
Thread 1: charger manager Thread 2: power supply driver, used by charger manager
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()
The 'get_property' callback is still valid and leads to actual calling of Thread2->get_property() but now in invalid context because the driver was unbound.
This could be observed easily with charger manager driver (here compiled with max17042 fuel gauge): $ echo "12-0036" > /sys/bus/i2c/drivers/max17042/unbind $ cat /sys/devices/virtual/power_supply/battery/temp [ 240.505998] INFO: task cat:1394 blocked for more than 120 seconds. [ 240.510762] Not tainted 3.17.0-next-20141007-00028-ge60b6dd79570-dirty #183 [ 240.518208] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 240.526025] cat D c0469548 0 1394 1 0x00000000 [ 240.532384] [<c0469548>] (__schedule) from [<c0469d54>] (schedule_preempt_disabled+0x14/0x20) [ 240.540885] [<c0469d54>] (schedule_preempt_disabled) from [<c046af20>] (mutex_lock_nested+0x1bc/0x458) [ 240.550171] [<c046af20>] (mutex_lock_nested) from [<c0287a98>] (regmap_read+0x30/0x60) [ 240.558079] [<c0287a98>] (regmap_read) from [<c032238c>] (max17042_get_property+0x2e8/0x350) [ 240.566490] [<c032238c>] (max17042_get_property) from [<c0324b60>] (charger_get_property+0x238/0x31c) [ 240.575688] [<c0324b60>] (charger_get_property) from [<c0320764>] (power_supply_show_property+0x48/0x1e0) [ 240.585241] [<c0320764>] (power_supply_show_property) from [<c027308c>] (dev_attr_show+0x1c/0x48) [ 240.594100] [<c027308c>] (dev_attr_show) from [<c0141fb0>] (sysfs_kf_seq_show+0x84/0x104) [ 240.602251] [<c0141fb0>] (sysfs_kf_seq_show) from [<c0140b18>] (kernfs_seq_show+0x24/0x28) [ 240.610497] [<c0140b18>] (kernfs_seq_show) from [<c0104574>] (seq_read+0x1b0/0x484) [ 240.618138] [<c0104574>] (seq_read) from [<c00e1e24>] (vfs_read+0x88/0x144) [ 240.625127] [<c00e1e24>] (vfs_read) from [<c00e1f20>] (SyS_read+0x40/0x8c) [ 240.631941] [<c00e1f20>] (SyS_read) from [<c000e760>] (ret_fast_syscall+0x0/0x48)
Or: [ 17.277605] Division by zero in kernel. [ 17.280043] CPU: 2 PID: 1384 Comm: cat Not tainted 3.17.0-next-20141007-00028-ge60b6dd79570-dirty #181 [ 17.289348] [<c00140f0>] (unwind_backtrace) from [<c0011228>] (show_stack+0x10/0x14) [ 17.297055] [<c0011228>] (show_stack) from [<c04680d0>] (dump_stack+0x70/0xbc) [ 17.304264] [<c04680d0>] (dump_stack) from [<c01f7a28>] (Ldiv0+0x8/0x10) [ 17.310933] [<c01f7a28>] (Ldiv0) from [<c01f79f8>] (__aeabi_uidivmod+0x8/0x18) [ 17.318132] [<c01f79f8>] (__aeabi_uidivmod) from [<c0287a84>] (regmap_read+0x1c/0x60) [ 17.325956] [<c0287a84>] (regmap_read) from [<c0322260>] (max17042_get_property+0x1bc/0x350) [ 17.334361] [<c0322260>] (max17042_get_property) from [<c0324734>] (charger_get_property+0x198/0x328) [ 17.343560] [<c0324734>] (charger_get_property) from [<c0320764>] (power_supply_show_property+0x48/0x1e0) [ 17.353108] [<c0320764>] (power_supply_show_property) from [<c03209d4>] (power_supply_uevent+0x9c/0x1c4) [ 17.362575] [<c03209d4>] (power_supply_uevent) from [<c02745d0>] (dev_uevent+0xb8/0x1c8) [ 17.370639] [<c02745d0>] (dev_uevent) from [<c0272c4c>] (uevent_show+0xa8/0x104) [ 17.378015] [<c0272c4c>] (uevent_show) from [<c027308c>] (dev_attr_show+0x1c/0x48) [ 17.385579] [<c027308c>] (dev_attr_show) from [<c0141fb0>] (sysfs_kf_seq_show+0x84/0x104) [ 17.393731] [<c0141fb0>] (sysfs_kf_seq_show) from [<c0140b18>] (kernfs_seq_show+0x24/0x28) [ 17.401979] [<c0140b18>] (kernfs_seq_show) from [<c0104574>] (seq_read+0x1b0/0x484) [ 17.409619] [<c0104574>] (seq_read) from [<c00e1e24>] (vfs_read+0x88/0x144) [ 17.416557] [<c00e1e24>] (vfs_read) from [<c00e1f20>] (SyS_read+0x40/0x8c) [ 17.423416] [<c00e1f20>] (SyS_read) from [<c000e760>] (ret_fast_syscall+0x0/0x48) [ 17.430880] power_supply battery: driver failed to report `voltage_now' property: -22
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com> Acked-by: Jonghwa Lee <jonghwa3.lee@samusng.com> Acked-by: Pavel Machek <pavel@ucw.cz> --- drivers/power/power_supply_core.c | 57 +++++++++++++++++++++++++++++++++++++-- include/linux/power_supply.h | 16 +++++++++++ 2 files changed, 71 insertions(+), 2 deletions(-)
diff --git a/drivers/power/power_supply_core.c b/drivers/power/power_supply_core.c index 6cb7fe5c022d..94f278cf2cbb 100644 --- a/drivers/power/power_supply_core.c +++ b/drivers/power/power_supply_core.c @@ -366,6 +366,56 @@ struct power_supply *power_supply_get_by_phandle(struct device_node *np, EXPORT_SYMBOL_GPL(power_supply_get_by_phandle); #endif /* CONFIG_OF */ +int power_supply_get_property(struct power_supply *psy, + enum power_supply_property psp, + union power_supply_propval *val) +{ + if (!psy->dev) + return -ENODEV; + + return psy->get_property(psy, psp, val); +} +EXPORT_SYMBOL_GPL(power_supply_get_property); + +int power_supply_set_property(struct power_supply *psy, + enum power_supply_property psp, + const union power_supply_propval *val) +{ + if (!psy->dev || !psy->set_property) + return -ENODEV; + + return psy->set_property(psy, psp, val); +} +EXPORT_SYMBOL_GPL(power_supply_set_property); + +int power_supply_property_is_writeable(struct power_supply *psy, + enum power_supply_property psp) +{ + if (!psy->dev || !psy->property_is_writeable) + return -ENODEV; + + return psy->property_is_writeable(psy, psp); +} +EXPORT_SYMBOL_GPL(power_supply_property_is_writeable); + +void power_supply_external_power_changed(struct power_supply *psy) +{ + if (!psy->dev || !psy->external_power_changed) + return; + + psy->external_power_changed(psy); +} +EXPORT_SYMBOL_GPL(power_supply_external_power_changed); + +void power_supply_set_charged(struct power_supply *psy) +{ + if (!psy->dev || !psy->set_charged) + return; + + psy->set_charged(psy); +} +EXPORT_SYMBOL_GPL(power_supply_set_charged); + int power_supply_powers(struct power_supply *psy, struct device *dev) { return sysfs_create_link(&psy->dev->kobj, &dev->kobj, "powers"); @@ -616,13 +666,16 @@ EXPORT_SYMBOL_GPL(power_supply_register_no_ws); void power_supply_unregister(struct power_supply *psy) { + struct device *dev = psy->dev; + cancel_work_sync(&psy->changed_work); sysfs_remove_link(&psy->dev->kobj, "powers"); + psy->dev = NULL; power_supply_remove_triggers(psy); psy_unregister_cooler(psy); psy_unregister_thermal(psy); - device_init_wakeup(psy->dev, false); - device_unregister(psy->dev); + device_init_wakeup(dev, false); + device_unregister(dev); } EXPORT_SYMBOL_GPL(power_supply_unregister); diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h index 3ed049673022..44e749c65505 100644 --- a/include/linux/power_supply.h +++ b/include/linux/power_supply.h @@ -189,6 +189,12 @@ struct power_supply { size_t num_supplies; struct device_node *of_node; + /* + * Functions for drivers implementing power supply class. + * These shouldn't be called directly by other drivers for accessing + * this power supply. Instead use power_supply_*() functions (for + * example power_supply_get_property()). + */ int (*get_property)(struct power_supply *psy, enum power_supply_property psp, union power_supply_propval *val); @@ -268,6 +274,16 @@ extern int power_supply_is_system_supplied(void); static inline int power_supply_is_system_supplied(void) { return -ENOSYS; } #endif +extern int power_supply_get_property(struct power_supply *psy, + enum power_supply_property psp, + union power_supply_propval *val); +extern int power_supply_set_property(struct power_supply *psy, + enum power_supply_property psp, + const union power_supply_propval *val); +extern int power_supply_property_is_writeable(struct power_supply *psy, + enum power_supply_property psp); +extern void power_supply_external_power_changed(struct power_supply *psy); +extern void power_supply_set_charged(struct power_supply *psy); extern int power_supply_register(struct device *parent, struct power_supply *psy); extern int power_supply_register_no_ws(struct device *parent, -- 1.9.1
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