Re: [PATCH] rcu: fix hotplug-cpu ->donelist leak

["Paul E. McKenney" <paulmck@us.ibm.com>]

On Tue, Jan 10, 2006 at 05:24:53PM +0300, Oleg Nesterov wrote:
> Pointed out by Srivatsa Vaddagiri <vatsa@in.ibm.com>.
> 
> rcu_do_batch() stops after processing maxbatch callbacks
> on ->donelist leaving rcu_tasklet in TASKLET_STATE_SCHED
> state.
> 
> If CPU_DEAD event happens remaining ->donelist entries are
> lost, rcu_offline_cpu() kills this tasklet.
> 
> With this patch ->donelist migrates along with ->curlist
> and ->nxtlist to the current cpu.
> 
> Compile tested.

This passed a ten-hour RCU torture test, with the torture test augmented
by Vatsa's CPU-hotplug RCU-torture-test patch.

							Thanx, Paul

Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
> Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
> 
> --- 2.6.15/kernel/rcupdate.c~4_HPFIX	2006-01-10 19:06:38.000000000 +0300
> +++ 2.6.15/kernel/rcupdate.c	2006-01-10 19:15:01.000000000 +0300
> @@ -343,8 +343,9 @@ static void __rcu_offline_cpu(struct rcu
>  	spin_unlock_bh(&rcp->lock);
>  	rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail);
>  	rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail);
> -
> +	rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail);
>  }
> +
>  static void rcu_offline_cpu(int cpu)
>  {
>  	struct rcu_data *this_rdp = &get_cpu_var(rcu_data);
>