On Wed, Oct 07, 2015 at 03:35:45PM +0200, Peter Zijlstra wrote:
> On Tue, Oct 06, 2015 at 09:29:23AM -0700, Paul E. McKenney wrote:
>
> > +/* Flags for rcu_preempt_ctxt_queue() decision table. */
> > +#define RCU_GP_TASKS 0x8
> > +#define RCU_EXP_TASKS 0x4
> > +#define RCU_GP_BLKD 0x2
> > +#define RCU_EXP_BLKD 0x1
>
> Purely cosmetic, but that's backwards ;-) Most of our flags etc.. are in
> increasing order.
>
> > +static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data
> > *rdp,
> > + unsigned long flags) __releases(rnp->lock)
> > +{
> > + int blkd_state = (rnp->gp_tasks ? RCU_GP_TASKS : 0) +
> > + (rnp->exp_tasks ? RCU_EXP_TASKS : 0) +
> > + (rnp->qsmask & rdp->grpmask ? RCU_GP_BLKD : 0) +
> > + (rnp->expmask & rdp->grpmask ? RCU_EXP_BLKD : 0);
>
> An alternative way is:
>
> int blkd_state = RCU_GP_TASKS * !!rnp->gp_tasks +
> RCU_EXP_TASKS * !!rnp->exp_tasks +
> RCU_GP_BLKD * !!(rnp->qsmask & rdp->grpmask) +
> RCU_EXP_BLKD * !!(rnp->expmask & rdp->grpmask);
>
> I suppose it depends on how your brain is wired which version reads
> easier :-)
Indeed! ;-)
I will stick with the ?: for the moment, but your multiplied bang-up
approach might well grow on me.
Thanx, Paul
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