On Sun, Sep 15, 2019 at 10:07:24AM -0700, Linus Torvalds wrote: > On Sun, Sep 15, 2019 at 7:32 AM Paul E. McKenney <paul...@kernel.org> wrote: > > > > First, what am I looking for? > > > > I am looking for something that prevents the following: > > > > o Task A acquires a reference to Task B's task_struct while > > protected only by RCU, and is just about to increment ->rcu_users > > when it is delayed. Maybe its vCPU is preempted or something. > > Where exactly do you see "increment ->rcu_users" > > There are _no_ users that can increment rcu_users. The thing is > initialized to '2' when the process is created, and nobody ever > increments it. EVER. > > It's only ever decremented, and when it hits zero we know that both > users are gone, and we start the rcu-delayed free.
Color me blind and apologies for the noise! Thanx, Paul