Messages in this thread | | | Date | Fri, 27 Jan 2006 21:42:41 -0600 | From | Nathan Lynch <> | Subject | Re: 2.6.16 - sys_sched_getaffinity & hotplug |
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Paul Jackson wrote: > Jack wrote: > > Should the following change be made to sched_getaffinity(). > > > > Index: linux/kernel/sched.c > > =================================================================== > > --- linux.orig/kernel/sched.c 2006-01-25 08:50:21.401747695 -0600 > > +++ linux/kernel/sched.c 2006-01-27 16:57:24.504871895 -0600 > > @@ -4031,7 +4031,7 @@ long sched_getaffinity(pid_t pid, cpumas > > goto out_unlock; > > > > retval = 0; > > - cpus_and(*mask, p->cpus_allowed, cpu_possible_map); > > + cpus_and(*mask, p->cpus_allowed, cpu_online_map); > > Adding Robert Love to the cc list, as he is Mr. sched_getaffinity, > I believe. > > I ended up doing a similar change, to the cpus (and mems) masks > in the root (all encompassing) cpuset.
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.
> These now show the values > of cpu_online_map and node_online_map, not *_MASK_ALL. > > My hunches are: > * This change to cpu_online_map is a good one.
It's not.
> * The man page sentence "Usually, all bits in the mask are set." > might have meant something when it was written, but it is not > now clear what.
I think it could reasonably be interpreted as all bits in the mask are set unless the task's affinity has been modified. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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