Re: [PATCH 5/5] workqueue: retry on NUMA_NO_NODE when create_worker() fails

KOSAKI Motohiro
2014-12-12T16:05:46Z

On Fri, Dec 12, 2014 at 5:19 AM, Lai Jiangshan <laijs@cn.fujitsu.com> wrote:
> A pwq bound to a specified node might be last long or even forever after
> the node was offline. Especially when this pwq has some back-to-back work
> items which requeue themselves and cause the pwq can't quit.
>
> This kinds of pwqs will cause their own pools busy and maybe create workers.
> This pools will fail on create_worker() since the node is offline.
>
> This case is extremely rare, but it is possible. And we hope create_worker()
> to be fault-tolerant in this case and other different cases when the node
> is lack of memory, for example, create_worker() can try to allocate memory
> from the whole system rather than only the target node, the most important
> thing is making some progress.
>
> So the solution is that, when the create_worker() fails on a specified node,
> it will retry with NUMA_NO_NODE for further allocation.

The code looks correct. But I don't think this issue depend on node offlining.
The allocation may also fail if node has no memory.