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? -- Uladzislau Rezki
