linux-kernel - Re: [PATCH 1/2] workqueue: Add new function mod_fwd_delayed

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Date:   Fri, 24 Feb 2017 00:22:37 +0100
From:   Harald Geyer <harald@...ib.org>
To:     Mark Brown <broonie@...nel.org>
cc:     Harald Geyer <harald@...ib.org>,
        Liam Girdwood <lgirdwood@...il.com>, Tejun Heo <tj@...nel.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] workqueue: Add new function mod_fwd_delayed_work()

Mark Brown writes:
> > > The obvious question here, especially in the case of
> > > mod_delayed_work(), is why not fix the existing functions to have
> > > the expected behaviour?
> 
> > AFAICS the existing functions behave as documented. I don't feel
> > to be an authority to decide that the documented behaviour is not
> > right. Actually I think that what mod_delayed_work() does, is a valid
> > operation, even if many current users probably don't want it.
> 
> It is *very* non-obvious that mod_delayed_work() will have a problem
> from the documentation, there's "mod_delayed_work_on() on local CPU"
> as the body of the description but honestly I'm struggling to tell if
> that's even there intentionally or anything other than an implementation
> detail. I'd expect to see some words describing the situations where it
> can be used or something, both the name and the lack of any information
> about issues suggest it's the default thing and will work safely.

It was obvious enough for me, so that I proposed a new function
instead of just switching the regulator code from queue_delayed_work()
to mod_delayed_work(). If it's not obvious to you, I suggest that
you supply a patch improving the documentation.

> > I was suprised when I found that no function like
> > mod_fwd_delayed_work() existed, so you have a point there.
> 
> I suspect people are just using mod_delayed_work(), not realising that
> there are restrictions. I'm thinking that perhaps it should be fixed to
> be safe for calling from different contexts and a new function with the
> existing behaviour added, that seems less error prone.

As I already wrote in my last message: To go that path means to review
107 uses of mod_delayed_work(). Maybe you have somebody you can assign
that task to? 

Harald
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