Messages in this thread | | | Date | Wed, 31 Aug 2022 11:47:55 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v6 4/5] sched: Handle set_cpus_allowed_ptr() & sched_setaffinity() race |
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On Thu, Aug 25, 2022 at 09:01:18PM -0400, Waiman Long wrote: > @@ -2722,6 +2734,7 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag > complete = true; > } > > + swap_user_cpus_ptr(p, puser_mask); > task_rq_unlock(rq, p, rf); > > if (push_task) { > @@ -2793,6 +2806,7 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag > if (flags & SCA_MIGRATE_ENABLE) > p->migration_flags &= ~MDF_PUSH; > > + swap_user_cpus_ptr(p, puser_mask); > task_rq_unlock(rq, p, rf); > > if (!stop_pending) { > @@ -2813,6 +2827,8 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag > complete = true; > } > } > + > + swap_user_cpus_ptr(p, puser_mask); > task_rq_unlock(rq, p, rf); > > if (complete)
I'm not at all sure about those.
Would it not be much simpler to keep the update of cpus_mask and cpus_user_mask together, always ensuring that cpus_user_mask is a strict superset of cpus_mask ? That is, set_cpus_allowed_common() seems like the right place to me.
I'm thinking this also means blowing away user_mask when we do a full reset of the cpus_mask when we do an affnity break.
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