Re: [PATCH 5/7] workqueue, use default pwq when fail to allocate node pwd

[Tejun Heo <tj@kernel.org>]

On Thu, Apr 04, 2013 at 10:05:36AM +0800, Lai Jiangshan wrote:
> When we fail to allocate the node pwq, we can use the default pwq
> for the node.
> 
> Thus we can avoid failure after allocated default pwq, and remove
> some code for failure path.

I don't know about this one.  The reason why we fall back to the
default one during CPU UP/DONW is because we don't want to interfere
with CPU hotplug which doesn't really have much to do with specific
workqueues and shouldn't fail even when things go pretty hairy -
e.g. if the user turned off the screen of his/her phone or a laptop is
thrown into the backpack with lid closed, CPU_DOWNs during suspend
better not fail from memory allocation.

apply_workqueue_attrs() is different.  We *want* to notify the issuer
that something went wrong affnd the action requested couldn't be
fulfilled in full.  We don't want to hide a failure.  It'll show up as
a silent performance degradation that nobody knows why it's happening.

So, nope, doesn't look like a good idea to me.

Thanks.

-- 
tejun