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However, the context is per executing cpu: the dispatch kfuncs > resolve it with this_cpu_ptr() and the dispatch buffer lives in it. What the > dispatches target is determined by the rq recorded in the context, not by > which cpu's context it is. Under core scheduling the pick runs balance_one() > for sibling rqs, so a sync processed for a sibling invokes the op with the > executing cpu's context not set up and its dispatch kfuncs misoperate on a > NULL or stale rq. > > Set up the executing cpu's dsp_ctx instead, matching scx_dispatch_sched(). > The recorded rq keeps the dispatches targeting the synced cpu. > > Fixes: b81a6c018cde ("sched_ext: Add sub_ecaps_updated() effective-cap change notifier") > Reported-by: David Carlier > Link: https://lore.kernel.org/all/20260813045931.8691-1-devnexen@gmail.com/ > Signed-off-by: Tejun Heo Everything looks correct to me. Reviewed-by: Andrea Righi Thanks, -Andrea > --- > kernel/sched/ext/sub.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > --- a/kernel/sched/ext/sub.c > +++ b/kernel/sched/ext/sub.c > @@ -1017,11 +1017,15 @@ void scx_process_sync_ecaps(struct rq *r > * invocation is equivalent to the dispatch path and may drop > * and re-acquire the rq lock temporarily while the rest of > * @batch is held privately, see scx_discard_ecaps_to_sync(). > + * The dispatch kfuncs resolve their context on the executing > + * cpu, which under core scheduling can differ from @rq's cpu, > + * so the context is set up there. The rq recorded in it keeps > + * the dispatches targeting @rq. > */ > if (ecaps != pcpu->reported_ecaps && > SCX_HAS_OP(pcpu->sch, sub_ecaps_updated) && > !scx_bypassing(pcpu->sch, cpu)) { > - struct scx_dsp_ctx *dspc = &pcpu->dsp_ctx; > + struct scx_dsp_ctx *dspc = &this_cpu_ptr(pcpu->sch->pcpu)->dsp_ctx; > > dspc->rq = rq; > /* stash @prev so nested dispatches can access it */ > > -- > 2.55.0