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    SubjectRe: [PATCH tip/core/rcu 06/23] rcu: Break up rcu_gp_kthread() into subfunctions
    On Thu, Sep 06, 2012 at 03:39:51PM +0200, Peter Zijlstra wrote:
    > 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?

    The kthread stops only when the system goes down, so no need for any
    kthread_stop() or kthread_park(). The "return 0" suppresses complaints
    about falling of the end of a non-void function.

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

    For those two loops, I suppose I could pull the cond_resched() and
    flush_signals() to the top, and make a do-while out of it.

    Thanx, Paul



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