On Mon, 18 Jul 2016 18:35:19 +0200, Benjamin Tissoires wrote: > On Jul 18 2016 or thereabouts, Jean Delvare wrote: > > But what happens on i2c_adapter removal? What prevents the following > > sequence from happening? > > > > 1* A Host Notify event happens. > > 2* The event is handled and queued by i2c_handle_smbus_host_notify(). > > 3* Someone tears down the underlying i2c_adapter (for example "rmmod > > i2c-i801".) > > 4* The workqueue is processed, accessing memory which has already been > > freed. > > > > Of course it would be back luck, but that's pretty much the definition > > of a race condition ;-) > > Yes, you are right :( > Sorry for not doing things properly :/ No worry. Bugs happen everywhere, we find them and fix them. That's part of the process. If we only submit patches which we are 100% certain are perfect, we never submit anything. I know something about that... > > To be on the safe side, don't we need a teardown function in i2c-smbus, > > that could be called before i2c_del_adapter, which would remove the > > host notify handle and flush the workqueue? > > I was thinking at adding a devm action on the release of the struct > smbus_host_notify, but it's actually a bad idea because some other > resources (children moslty) might already be released when the devres > action will be called. > > I think it might be easier to add a i2c_remove_host_notify() (or such) > which would make sure we call the cancel_work_sync() function. It would > be the responsibility of the caller to call it once > i2c_setup_smbus_host_notify() has been called. I'd say it has the > advantage of not adding any hidden data in the adapter to the cost of a > small pain in the adapter driver. That's what I had in mind as well, but I'm open to any option which solves the problem really. -- Jean Delvare SUSE L3 Support -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
