On Fri, Aug 15, 2025 at 03:40:16PM +0200, Peter Zijlstra wrote: > On Wed, Aug 06, 2025 at 10:01:20AM +0200, Nam Cao wrote: > > > +/* > > + * The two trace points below may not work as expected for fair tasks due > > + * to delayed dequeue. See: > > + * > > https://lore.kernel.org/lkml/[email protected]/ > > + */ > > > +DECLARE_TRACE(dequeue_task, > > + TP_PROTO(int cpu, struct task_struct *task), > > + TP_ARGS(cpu, task)); > > + > > > @@ -2119,7 +2121,11 @@ inline bool dequeue_task(struct rq *rq, struct > > task_struct *p, int flags) > > * and mark the task ->sched_delayed. > > */ > > uclamp_rq_dec(rq, p); > > - return p->sched_class->dequeue_task(rq, p, flags); > > + if (p->sched_class->dequeue_task(rq, p, flags)) { > > + trace_dequeue_task_tp(rq->cpu, p); > > + return true; > > + } > > + return false; > > } > > Hurmpff.. that's not very nice. > > How about something like: > > dequeue_task(): > ... > ret = p->sched_class->dequeue_task(rq, p, flags); > if (trace_dequeue_task_p_enabled() && !(flags & DEQUEUE_SLEEP)) > __trace_dequeue_task_tp(rq->cpu, p); > return ret; > > > __block_task(): > trace_dequeue_task_tp(rq->cpu, p); > ... > > > Specifically, only DEQUEUE_SLEEP is allowed to fail, and DEQUEUE_SLEEP > will eventually cause __block_task() to be called, either directly, or > delayed.
Thanks for the suggestion, this makes sense. >From my understanding, it makes the tracepoints work correctly for fair tasks too, so I will get rid of the comment. Nam
