Messages in this thread | | | Date | Fri, 27 Jan 2006 23:23:56 -0600 | From | Nathan Lynch <> | Subject | Re: 2.6.16 - sys_sched_getaffinity & hotplug |
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Paul Jackson wrote: > Nathan wrote: > > Which is problematic, because cpuset_cpus_allowed -> > > guarantee_online_cpus restricts the task->cpus_allowed mask to cpus > > which happen to be online at the time of the call to > > sched_setaffinity. If more cpus come online later, that task can't be > > migrated to them. > > Well, sort of. > > A task could always migrate - just because a sched_getaffinity > the task did in the past doesn't show a CPU as valid, doesn't stop > the task from asking to pin to that CPU now.
I was speaking of the setaffinity (not getaffinity) case -- I assumed this was what you were referring to since I couldn't find any calls to the cpuset code in the getaffinity path.
> One of three lessons could be taken from your example: > 1) return all possible CPUS (CPU_MASK_ALL, likely), as you > recommend
I'm only recommending not changing the current behavior of sched_getaffinity.
(BTW - cpu_possible_map can be a subset of CPU_MASK_ALL on some platforms -- powerpc, at least, since we can discover the number of truly possible cpus early in boot.)
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