lkml.org 
[lkml]   [2010]   [Feb]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [regression] cpuset,mm: update tasks' mems_allowed in time (58568d2)
On Tue, 23 Feb 2010, Miao Xie wrote:

> > Cpu hotplug sets top_cpuset's cpus_allowed to cpu_active_mask by default,
> > regardless of what was onlined or offlined. cpus_attach in the context of
> > your patch (in cpuset_attach()) passes cpu_possible_mask to
> > set_cpus_allowed_ptr() if the task is being attached to top_cpuset, my
> > question was why don't we pass cpu_active_mask instead? In other words, I
> > think we should do
> >
> > cpumask_copy(cpus_attach, cpu_active_mask);
> >
> > when attached to top_cpuset like my patch did.
>
> If we pass cpu_active_mask to set_cpus_allowed_ptr(), task->cpus_allowed just contains
> the online cpus. In this way, if we do cpu hotplug(such as: online some cpu), we must
> update cpus_allowed of all tasks in the top cpuset.
>
> But if we pass cpu_possible_mask, we needn't update cpus_allowed of all tasks in the
> top cpuset. And when the kernel looks for a cpu for task to run, the kernel will use
> cpu_active_mask to filter out offline cpus in task->cpus_allowed. Thus, it is safe.
>

That is terribly inconsistent between top_cpuset and all descendants; all
other cpusets require that task->cpus_allowed be a subset of
cpu_online_mask, including those descendants that allow all cpus (and all
mems).


\
 
 \ /
  Last update: 2010-02-23 23:35    [W:0.358 / U:0.168 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site