Messages in this thread | | | Date | Thu, 6 Sep 2012 11:49:21 -0700 | From | Josh Triplett <> | Subject | Re: [PATCH tip/core/rcu 06/23] rcu: Break up rcu_gp_kthread() into subfunctions |
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On Thu, Sep 06, 2012 at 10:32:07AM -0700, Paul E. McKenney wrote: > 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.
Huh, I thought GCC knew to not emit that warning unless it actually found control flow reaching the end of the function; since the infinite loop has no break in it, you shouldn't need the return. Annoying.
> > 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.
I think it makes more sense to move the wait_event_interruptible to the bottom, and make a while out of it.
- Josh Triplett
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