Hi Hans, Thanks for your report. I'll check this problem and try to resolve it.
On 2016년 12월 22일 00:54, Hans de Goede wrote: > Hi, > > With the recent extcon work I've been doing I noticed that > if I want to rmmod and then insmod say extcon_axp288 I can > do so without problems even if axp288_charger is holding > a reference to the extcon device returned by extcon_get_extcon_dev. > > The problem is that extcon_get_extcon_dev simply looks up > the extcon-device in the list of current registered extcon-s > and then returns a pointer to it, without any reference > counting. > > The rmmod scenario can be fixed by doing a module_get from > extcon_get_extcon_dev, but that still leaves the same problem > when root manually unbinds the driver through sysfs. > > A possible way fix this would be: > > 1) Make all extcon providers use devm_extcon_dev_allocate and document > using this to allocate an extcon_dev mandatory > > 2) Add a refcount to struct extcon_dev and introduce extcon_dev_get > and extcon_dev_put helpers which modify the refcount and only free > the memory on the final put (and make the evm_extcon_dev_allocate > cleanup function call extcon_dev_put) > > 3) On extcon_dev_unregister set a flag in the extcon_dev that it > has been free-ed, make all extcon consumer functions which take > an extcon_dev (extcon_get_state, extcon_register_notifier, etc.) > check this flag and return -ENODEV when the extcon has been unregistered > > 4) Make extcon_get_extcon_dev call extcon_dev_get on the returned edev > before returning it > > From here on we've fixed the crash, but we now leak the extcon_dev > when the consumer gets unbound. > > 5) Add a devm_extcon_get_extcon_dev which calls extcon_dev_put as the devm > cleanup function > > 6) Convert all extcon consumers to use devm_extcon_get_extcon_dev > > Regards, > > Hans > > > -- Regards, Chanwoo Choi
