* Tejun Heo <t...@kernel.org> wrote:
> PF_THREAD_BOUND was originally used to mark kernel threads which were
> bound to a specific CPU using kthread_bind() and a task with the flag
> set allows cpus_allowed modifications only to itself. Workqueue is
> currently abusing it to prevent userland from meddling with
> cpus_allowed of workqueue workers.
>
> What we need is a flag to prevent userland from messing with
> cpus_allowed of certain kernel tasks. In kernel, anyone can
> (incorrectly) squash the flag, and, for worker-type usages,
> restricting cpus_allowed modification to the task itself doesn't
> provide meaningful extra proection as other tasks can inject work
> items to the task anyway.
>
> This patch replaces PF_THREAD_BOUND with PF_NO_SETAFFINITY.
> sched_setaffinity() checks the flag and return -EINVAL if set.
> set_cpus_allowed_ptr() is no longer affected by the flag.
>
> This will allow simplifying workqueue worker CPU affinity management.
Acked-by: Ingo Molnar <mi...@kernel.org>
I suspect you want to carry this in the workqueue tree, to enable those
extra simplifications?
Thanks,
Ingo
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