Re: [patch] sched: prevent bound kthreads from changing cpus_allowed

[Paul Jackson <pj@sgi.com>]

A couple of questions on this:

 1) Sometimes threads are bound to a set of CPUs, such as the CPUs
    on a particular node:

	drivers/pci/pci-driver.c:       set_cpus_allowed_ptr(current, nodecpumask);
	net/sunrpc/svc.c:               set_cpus_allowed_ptr(current, nodecpumask);

    Such cases can't invoke kthread_bind(), as that only binds to a single CPU.
    I only see one place in your patch that sets PF_THREAD_BOUND; would it make
    sense for such multi-CPU binds as above to be PF_THREAD_BOUND as well?

 2) Sometimes calls to kthread_bind are binding to any online cpu, such as in:

	drivers/infiniband/hw/ehca/ehca_irq.c:	kthread_bind(cct->task, any_online_cpu(cpu_online_map));

    In such cases, the PF_THREAD_BOUND seems inappropriate.  The caller of
    kthread_bind() really doesn't seem to care where that thread is bound;
    they just want it on a CPU that is still online.

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                  Paul Jackson <pj@sgi.com> 1.940.382.4214