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This mirrors > what scx_vet_enq_flags() does for BPF callers. > > Fixes: 3229ac4a5ef5 ("sched_ext: Add SCX_OPS_ALWAYS_ENQ_IMMED ops flag") > Signed-off-by: zhidao su > --- > v2: Resend to correct a submission error in v1 where unrelated files > were accidentally included in the patch. The code change is > identical; only kernel/sched/ext.c is modified. Apologies for > the noise. > --- > kernel/sched/ext.c | 15 ++++++++++++++- > 1 file changed, 14 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c > index 9628c64e5592..0758f5e5a8f0 100644 > --- a/kernel/sched/ext.c > +++ b/kernel/sched/ext.c > @@ -1859,7 +1859,9 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags, > * Clear persistent TASK_IMMED for fresh enqueues, see dsq_inc_nr(). > * Note that exiting and migration-disabled tasks that skip > * ops.enqueue() below will lose IMMED protection unless > - * %SCX_OPS_ENQ_EXITING / %SCX_OPS_ENQ_MIGRATION_DISABLED are set. > + * %SCX_OPS_ENQ_EXITING / %SCX_OPS_ENQ_MIGRATION_DISABLED are set, > + * or %SCX_OPS_ALWAYS_ENQ_IMMED is enabled (which re-applies IMMED > + * at the enqueue: label below). > */ > p->scx.flags &= ~SCX_TASK_IMMED; > > @@ -1949,6 +1951,17 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags, > */ > touch_core_sched(rq, p); > refill_task_slice_dfl(sch, p); > + > + /* > + * Honor %SCX_OPS_ALWAYS_ENQ_IMMED for framework-internal local DSQ > + * enqueues (PF_EXITING, migration-disabled, !online fallbacks). > + * scx_vet_enq_flags() already handles this for BPF kfunc callers, > + * but the goto-local paths above bypass it. > + */ > + if ((sch->ops.flags & SCX_OPS_ALWAYS_ENQ_IMMED) && > + dsq == &rq->scx.local_dsq) > + enq_flags |= SCX_ENQ_IMMED; > + I'm not sure this should be applied across all fallback cases, it's probably safer to avoid triggering re-enqueues for the internal events, especially considering that the BPF scheduler doesn't have visibility into them. If we do this we should also update %SCX_ENQ_IMMED documentation, that says: * Exiting and migration-disabled tasks bypass ops.enqueue() and * are placed directly on a local DSQ without IMMED protection * unless %SCX_OPS_ENQ_EXITING and %SCX_OPS_ENQ_MIGRATION_DISABLED * are set respectively. But again, do we actually want to do this? If SCX_OPS_ENQ_EXITING and SCX_OPS_ENQ_MIGRATION_DISABLED aren't set, these cases are handled internally by the sched_ext core, so triggering a re-enqueue seems unnecessary, as the BPF scheduler wouldn't have visibility of such events anyway. > dispatch_enqueue(sch, rq, dsq, p, enq_flags); > } > > -- > 2.43.0 > Thanks, -Andrea