Re: [PATCH 3/5] workqueue: ensure attrs-changing be sequentially

[Tejun Heo <tj@kernel.org>]

Hello,

On Tue, May 12, 2015 at 01:09:50PM +0800, Lai Jiangshan wrote:
> On 05/11/2015 10:55 PM, Tejun Heo wrote:
> >>
> >> Process A (change cpumask)	| Process B (change numa affinity)
> >> wq_cpumask_store()		|
> >>   wq_sysfs_prep_attrs()		|
> > 				^
> > 				misaligned
> 
> It is aligned in email, misaligned in quoted email, and misaligned
> in `git log` and `git show`, aligned in `git commit` when I wrote
> the changelog. 
> 
> I will just remove all the |.

Hmmm... I wonder why that is.  It looks consistently misaligned here.
If in doubt, just use spaces instead of tabs when drawing stuff.

...
> >> Sequential model on non-performance-sensitive operations is more popular
> >> and preferred. So this patch moves wq_sysfs_prep_attrs() into the protection
> > 
> > You can just say the previous behavior is buggy.
> 
> It depends on definitions. To me, it is just a nuisance.

I find this pretty difficult to agree with.  A does an operation which
changes attribute 1.  B independently tries to change attribute 2.
Depending on the sequence, we end up with three different results.
How is this not a bug?

Thanks.

-- 
tejun