> On pon, 2014-09-29 at 04:25 +0000, 함명주 wrote: > > > > > > Kernel built with extcon and charger-manager. > > > > > > After connecting the USB cable sleeping function was called from atomic > > > context: > > > [ 63.328648] BUG: sleeping function called from invalid context at > > > kernel/locking/mutex.c:586 > > [] > > > [ 63.388743] Workqueue: events max14577_muic_irq_work > > > [ 63.393707] [<c00167a4>] (unwind_backtrace) from [<c0012c08>] > > > (show_stack+0x10/0x14) > > > [ 63.401422] [<c0012c08>] (show_stack) from [<c06232ec>] > > > (dump_stack+0x70/0xbc) > > > [ 63.408625] [<c06232ec>] (dump_stack) from [<c0629d0c>] > > > (mutex_lock_nested+0x24/0x410) > > > [ 63.416525] [<c0629d0c>] (mutex_lock_nested) from [<c0354474>] > > > (regmap_read+0x30/0x60) > > > [ 63.424424] [<c0354474>] (regmap_read) from [<c0406b84>] > > > (max14577_charger_get_property+0x1e4/0x250) > > > [ 63.433535] [<c0406b84>] (max14577_charger_get_property) from > > > [<c0403834>] (is_ext_pwr_online+0x30/0x6c) > > > [ 63.442994] [<c0403834>] (is_ext_pwr_online) from [<c0404a54>] > > > (charger_extcon_notifier+0x40/0x70) > > > [ 63.451934] [<c0404a54>] (charger_extcon_notifier) from [<c044cbe4>] > > > (_call_per_cable+0x40/0x4c) > > > [ 63.460704] [<c044cbe4>] (_call_per_cable) from [<c0051560>] > > > (notifier_call_chain+0x64/0x128) > > > [ 63.469209] [<c0051560>] (notifier_call_chain) from [<c0051640>] > > > (raw_notifier_call_chain+0x18/0x20) > > > [ 63.478321] [<c0051640>] (raw_notifier_call_chain) from [<c044d0fc>] > > > (extcon_update_state+0xa8/0x204) > > > [ 63.487522] [<c044d0fc>] (extcon_update_state) from [<c044e5f8>] > > > (max14577_muic_chg_handler+0xdc/0x180) > > > [ 63.496897] [<c044e5f8>] (max14577_muic_chg_handler) from [<c044e924>] > > > (max14577_muic_irq_work+0x7c/0xd8) > > > [ 63.506445] [<c044e924>] (max14577_muic_irq_work) from [<c004480c>] > > > (process_one_work+0x198/0x66c) > > > [ 63.515385] [<c004480c>] (process_one_work) from [<c0044d4c>] > > > (worker_thread+0x38/0x564) > > > [ 63.523455] [<c0044d4c>] (worker_thread) from [<c004c4ec>] > > > (kthread+0xcc/0xe8) > > > [ 63.530661] [<c004c4ec>] (kthread) from [<c000f1f8>] > > > (ret_from_fork+0x14/0x3c) > > > [ 63.543926] charger_manager: Set current limit of CHARGER : 450000uA ~ > > > 450000uA > > > [ 63.548870] extcon-port jack: jack event CHGDET=usb > > > [ 63.550592] extcon-port jack: jack event CHGDET=charger > > > [ 64.188607] charger-manager charger-manager@0: Failed to get battery > > > temperature > > > [ 64.200684] charger-manager charger-manager@0: CHARGING > > > > > > The first sleeping function is is_ext_pwr_online() > > > (drivers/power/charger-manager.c). The atomic context initiating the > > > flow is set up in extcon_update_state() (drivers/extcon/extcon-class.c). > > > > > > The extcon_update_state() uses spin locks which are not necessary > > > because the function is not called from interrupt service routines. > > > Instead, the extcon_update_state() is called from: > > > 1. Threaded interrupt handlers. > > > 2. Work queues. > > > > > > Replace the spin lock with mutex and update the documentation of this > > > function. > > > > No. You've done it in the opposite way. > > > > update_state is often called in a interrupt handler that cannot sleep. > > > > For the context you've mentioned, we'd need workqueue invoked by > > _call_per_cable or notifier callback. > > I'm still not convinced that calling raw_notifier_chain under spin lock > in extcon_update_state() is safe. I think it is not safe because current > design implies silently that all notifiers registered with > extcon_register_notifier() must not sleep.
Even if we remove spin_lock completely, whenever an interrupt handler notifies state change via extcon, you will get the similar BUG messages. The mutex of I2C won't work in that context. > > _call_per_cable() is just one of ways to trigger this issue. > Thus, in order to satisfy both interrupt handlers and sleeping notifyees, we can add an option to let _call_per_cable() use workqueue for those who want to sleep. Cheers, MyungJoo
