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SubjectRe: [PATCH] cgroup/cpuset: fix circular locking dependency
Hello, Prateek.

On Wed, Dec 13, 2017 at 01:20:46PM +0530, Prateek Sood wrote:
> This change makes the usage of cpuset_hotplug_workfn() from cpu
> hotplug path synchronous. For memory hotplug it still remains
> asynchronous.

Ah, right.

> Memory migration happening from cpuset_hotplug_workfn() is
> already asynchronous by queuing cpuset_migrate_mm_workfn() in
> cpuset_migrate_mm_wq.
>
> cpuset_hotplug_workfn()
> cpuset_hotplug_workfn(()
> cpuset_migrate_mm()
> queue_work(cpuset_migrate_mm_wq)
>
> It seems that memory migration latency might not have
> impact with this change.
>
> Please let me know if you meant something else by cpuset
> migration taking time when memory migration is turned on.

No, I didn't. I was just confused about which part became
synchronous. So, I don't have anything against making the cpu part
synchronous, but let's not do that as the fix to the deadlocks cuz,
while we can avoid them by changing cpuset, I don't think cpuset is
the root cause for them. If there are benefits to making cpuset cpu
migration synchronous, let's do that for those benefits.

Thanks.

--
tejun

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