linux-kernel - Re: [PATCH tip/core/rcu 06/23] rcu: Break up rcu_gp

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Date:	Thu, 06 Sep 2012 15:39:51 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, josh@...htriplett.org,
	niv@...ibm.com, tglx@...utronix.de, rostedt@...dmis.org,
	Valdis.Kletnieks@...edu, dhowells@...hat.com,
	eric.dumazet@...il.com, darren@...art.com, fweisbec@...il.com,
	sbw@....edu, patches@...aro.org
Subject: Re: [PATCH tip/core/rcu 06/23] rcu: Break up rcu_gp_kthread() into
 subfunctions

On Thu, 2012-08-30 at 11:18 -0700, Paul E. McKenney wrote:
> +static int rcu_gp_kthread(void *arg)
> +{
> +       struct rcu_state *rsp = arg;
> +       struct rcu_node *rnp = rcu_get_root(rsp);
> +
> +       for (;;) {
> +
> +               /* Handle grace-period start. */
> +               for (;;) {
> +                       wait_event_interruptible(rsp->gp_wq, rsp->gp_flags);
> +                       if (rsp->gp_flags && rcu_gp_init(rsp))
> +                               break;
> +                       cond_resched();
> +                       flush_signals(current);
> +               }
>  
>                 /* Handle grace-period end. */
>                 for (;;) {
>                         wait_event_interruptible(rsp->gp_wq,
>                                                  !ACCESS_ONCE(rnp->qsmask) &&
>                                                  !rcu_preempt_blocked_readers_cgp(rnp));
>                         if (!ACCESS_ONCE(rnp->qsmask) &&
> +                           !rcu_preempt_blocked_readers_cgp(rnp) &&
> +                           rcu_gp_cleanup(rsp))
>                                 break;
> +                       cond_resched();
>                         flush_signals(current);
>                 }
>         }
>         return 0;
>  } 

Should there not be a kthread_stop() / kthread_park() call somewhere in
there?

Also, it could be me, but all those nested for (;;) loops make the flow
rather non-obvious.
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