On Wed, Jan 20, 2021 at 12:42 PM Xie He <xie.he.0141@xxxxxxxxx> wrote: > > With this patch, there is still a problem that lapb_unregister may run > concurrently with other LAPB API functions (such as > lapb_data_received). This other LAPB API function can get the > lapb->lock after lapb->lock is released by lapb_unregister, and > continue to do its work. This is not correct. > > We can fix this problem by adding a new field "bool stop" to "struct > lapb_cb" (just like "bool t1timer_stop, t2timer_stop"), and make every > API function abort whenever it sees lapb->stop == true after getting > the lock. > > Alternatively we can also require the callers (the LAPB drivers) to > never call lapb_unregister concurrently with other LAPB APIs. They > should make sure all LAPB API functions are only called after > lapb_register ends and before lapb_unregister starts. This is a > reasonable requirement, because if they don't follow this requirement, > even if we do the fix in the LAPB module (as said above), the LAPB > driver will still get the "LAPB_BADTOKEN" error from the LAPB module. > This is not desirable and I think LAPB drivers should avoid this from > happening. > > So I think this problem may not need to be fixed here in the LAPB > module because the LAPB drivers should deal with this problem anyway. Never mind, I have sent a v5 to deal with this problem. In v5, I made lapb_unregister wait for the "lapb" refcnt to drop, so that we can make sure all other API calls have finished. Please see my v5.
