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    SubjectRe: [PATCH tip/core/rcu 01/23] rcu: Move RCU grace-period initialization into a kthread
    On Thu, Sep 06, 2012 at 03:32:22PM +0200, Peter Zijlstra wrote:
    > On Thu, 2012-08-30 at 11:18 -0700, Paul E. McKenney wrote:
    > > +static int rcu_gp_kthread(void *arg)
    > > +{
    > > + unsigned long flags;
    > > + struct rcu_data *rdp;
    > > + struct rcu_node *rnp;
    > > + struct rcu_state *rsp = arg;
    > > +
    > > + for (;;) {
    > > +
    > > + /* Handle grace-period start. */
    > > + rnp = rcu_get_root(rsp);
    > > + for (;;) {
    > > + wait_event_interruptible(rsp->gp_wq, rsp->gp_flags);
    > > + if (rsp->gp_flags)
    > > + break;
    > > + flush_signals(current);
    > > + }
    > > + raw_spin_lock_irqsave(&rnp->lock, flags);
    >
    > You're in a kthread, it should be impossible for IRQs to be disabled
    > here, no? Similar for most (all) other sites in this function.
    >
    > Using the unconditional IRQ disable/enable is generally faster.

    I suppose I could see my way to using raw_spin_lock_irq() here. ;-)

    Thanx, Paul



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