Re: [PATCH] cpusets: rework guarantee_online_cpus() to fix deadlockwith cpu_down()

[Lai Jiangshan]

Oleg Nesterov wrote:

> 
> 	- do NOT scan cs->parent cpusets. If there are no online CPUs in
> 	  cs->cpus_allowed, we use cpu_online_mask. This is only possible
> 	  when we are called by cpu_down() hooks, in that case
> 	  cpuset_track_online_cpus(CPU_DEAD) will fix things later.
> 


We must scan cs->parent cpusets.
A task is constrained by a cpuset, it must be constrained
this cpuset's parent too.

cpuset_lock() is not awful at all.

Lai.


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