Re: [PATCH 12/18] sched_ext: Generalize the reject DSQ reenqueue path

[Andrea Righi]

Hi Tejun,

On Thu, Sep 03, 2026 at 12:39:20PM -1000, Tejun Heo wrote:
> Hello,
> 
> Nits follow.
> 
> On Mon, Aug 31, 2026 at 03:42:22PM +0200, Andrea Righi wrote:
> > @@ -1599,11 +1599,10 @@ static void scx_dispatch_enqueue(struct scx_sched *sch, struct rq *rq,
> >  				 struct scx_dispatch_q *dsq, struct task_struct *p,
> >  				 u64 slice, u64 vtime, u64 enq_flags)
> >  {
> > -	bool is_rq_owned = false;
> > +	bool is_rq_owned = dsq_is_rq_owned(dsq);
> >  
> >  	if (dsq->id == SCX_DSQ_LOCAL) {
> >  		dsq = scx_resolve_local_dsq(sch, rq, p, &enq_flags);
> > -		is_rq_owned = true;
> >  	}
> 
> No need for {}.
> 
> > @@ -2017,6 +2016,7 @@ void scx_do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,
> >  			__scx_exit(sch, SCX_EXIT_ERROR_REENQ, 0, cpu_of(rq),
> >  				   "%s[%d] reenqueued %u times without running",
> >  				   p->comm, p->pid, p->scx.reenq_cnt);
> > +			p->scx.flags &= ~SCX_TASK_REENQ_REASON_MASK;
> >  			return;
> >  		}
> >  	}
> > @@ -2067,6 +2067,8 @@ void scx_do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,
> >  
> >  	SCX_CALL_OP_TASK(sch, enqueue, rq, p, enq_flags);
> >  
> > +	/* The reason is input to ops.enqueue(), not to the resulting placement. */
> > +	p->scx.flags &= ~SCX_TASK_REENQ_REASON_MASK;
> >  	*ddsp_taskp = NULL;
> >  	if (p->scx.ddsp_dsq_id != SCX_DSQ_INVALID)
> >  		goto direct;
> > @@ -2085,9 +2087,11 @@ void scx_do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,
> >  	return;
> >  
> >  direct:
> > +	p->scx.flags &= ~SCX_TASK_REENQ_REASON_MASK;
> >  	direct_dispatch(sch, p, enq_flags);
> >  	return;
> >  local_norefill:
> > +	p->scx.flags &= ~SCX_TASK_REENQ_REASON_MASK;
> >  	scx_dispatch_enqueue(sch, rq, &rq->scx.local_dsq, p, 0, 0, enq_flags);
> >  	return;
> >  local:
> > @@ -2101,6 +2105,7 @@ void scx_do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,
> >  	goto enqueue;
> >  
> >  enqueue:
> > +	p->scx.flags &= ~SCX_TASK_REENQ_REASON_MASK;
> >  	refill_task_slice_dfl(sch, p);
> >  	clear_direct_dispatch(p);
> >  	scx_dispatch_enqueue(sch, rq, dsq, p, 0, 0, enq_flags);
> 
> This is too messy. The clearing is scattered all over and sometimes done
> twice. Can't you add one label that everyone jumps to for exit and clear it
> there?
> 
> Thanks.

Ack to all the nits, I'll clean them up.

Thanks,
-Andrea