On Wed, Feb 26, 2025 at 09:48:52PM +0100, Uladzislau Rezki wrote: > Hello, Boqun. > > > Hi Ulad, > > > > On Tue, Feb 25, 2025 at 12:00:20PM +0100, Uladzislau Rezki (Sony) wrote: > > > Switch for using of get_state_synchronize_rcu_full() and > > > poll_state_synchronize_rcu_full() pair for debug a normal > > > synchronize_rcu() call. > > > > > > Just using "not" full APIs to identify if a grace period > > > is passed or not might lead to a false kernel splat. > > > > > > > Could you provide detailed explanation on this? I.e. why is _full() is > > needed? I find the current commit message is a bit vague. > > > <snip> > rcu: Use _full() API to debug synchronize_rcu() > > Switch for using of get_state_synchronize_rcu_full() and > poll_state_synchronize_rcu_full() pair to debug a normal > synchronize_rcu() call. > > Just using "not" full APIs to identify if a grace period is > passed or not might lead to a false-positive kernel splat. > > It can happen, because get_state_synchronize_rcu() compresses > both normal and expedited states into one single unsigned long > value, so a poll_state_synchronize_rcu() can miss GP-completion > when synchronize_rcu()/synchronize_rcu_expedited() concurrently > run. > > To address this, switch to poll_state_synchronize_rcu_full() and > get_state_synchronize_rcu_full() APIs, which use separate variables > for expedited and normal states. > <snip> > > Does it look better? >
Yes, that looks good to me. Thanks! Regards, Boqun > -- > Uladzislau Rezki >
