Messages in this thread | | | Date | Wed, 4 Jun 2008 12:01:11 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [PATCH 2/2] cpusets: update tasks' cpus_allowed and mems_allowed after CPU/NODE offline/online |
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On Wed, 4 Jun 2008, Paul Jackson wrote:
> Do we need a new PF_* flag for this? Perhaps one can test for this > by examining the currently available properties of tasks. Would it > be sufficient to look for kernel threads (NULL mm_struct) whose > cpus_allowed is a strict subset of the online CPUs? >
That would only identify kthreads that have been created with a subsequent call to set_cpus_allowed() or kthread_bind().
The PF_CPU_BOUND change targets only the latter since there are kthreads, such as kstopmachine, that can continue to manipulate their cpus_allowed during their lifetime.
Other kthreads such as the scheduler migration thread and soft lockup watchdog thread, however, always stay bound to a single cpu by use of kthread_bind(). These are the tasks that get the PF_CPU_BOUND flag and cannot be rebound via set_cpus_allowed() because of their negative effects.
David
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