Messages in this thread | | | Date | Thu, 16 Mar 2017 16:02:34 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 2/2] kthread, cgroup: close race window where new kthreads can be migrated to non-root cgroups |
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On 03/15, Tejun Heo wrote: > > --- a/kernel/cgroup/cgroup.c > +++ b/kernel/cgroup/cgroup.c > @@ -2425,11 +2425,13 @@ ssize_t __cgroup_procs_write(struct kern > tsk = tsk->group_leader; > > /* > - * Workqueue threads may acquire PF_NO_SETAFFINITY and become > - * trapped in a cpuset, or RT worker may be born in a cgroup > - * with no rt_runtime allocated. Just say no. > + * kthreads may acquire PF_NO_SETAFFINITY during initialization. > + * If userland migrates such kthread to a non-root cgroup, it can > + * become trapped in a cpuset, or RT kthread may be born in a > + * cgroup with no rt_runtime allocated. Just say no. > */ > - if (tsk == kthreadd_task || (tsk->flags & PF_NO_SETAFFINITY)) { > + if (tsk == kthreadd_task || (tsk->flags & PF_NO_SETAFFINITY) || > + ((tsk->flags & PF_KTHREAD) && !kthread_initialized(tsk))) { > ret = -EINVAL;
...
> +bool kthread_initialized(struct task_struct *k) > +{ > + struct kthread *kthread = to_kthread(k); > + > + return kthread && test_bit(KTHREAD_INITIALIZED, &kthread->flags); > +}
Not sure I understand...
With this patch you can no longer migrate a kernel thread created by kernel_thread() ? Note that to_kthread() is NULL unless it was created by kthread_create().
Oleg.
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