Messages in this thread | | | Date | Tue, 13 Oct 2020 16:21:08 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 1/2] sched: Deny self-issued __set_cpus_allowed_ptr() when migrate_disable() |
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On Tue, Oct 13, 2020 at 04:15:08PM +0200, Sebastian Andrzej Siewior wrote: > On 2020-10-13 15:01:15 [+0100], Valentin Schneider wrote: > > migrate_disable(); > > set_cpus_allowed_ptr(current, {something excluding task_cpu(current)}); > > affine_move_task(); <-- never returns > > > > Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> > > --- > > kernel/sched/core.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > index 4ccd1099adaa..7f4e38819de1 100644 > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -2189,6 +2189,11 @@ static int __set_cpus_allowed_ptr(struct task_struct *p, > > if (!(flags & SCA_MIGRATE_ENABLE) && cpumask_equal(&p->cpus_mask, new_mask)) > > goto out; > > > > + if (p == current && > > + is_migration_disabled(p) && > > + !cpumask_test_cpu(task_cpu(p), new_mask)) > > + ret = -EBUSY; > > + > > This shouldn't happen, right? The function may sleep so it shouldn't be > entered with disabled migration. A WARN_ON might spot the bad caller.
So yeah, I like detecting the case but agree with bigeasy that an additional WARN would make sense, lemme go add that.
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