On Tue, 2010-12-14 at 15:19 +0100, Tejun Heo wrote:
> Hello, James.
>
> On 12/14/2010 03:09 PM, James Bottomley wrote:
> > That's the point ... it's purely for operations which require user
> > context which may not have it. There's no synchronisation by design
> > (it's a simple API).
>
> Well, the problem is that you do require proper synchornization
> anyway; otherwise, there is no way to make sure that the work is
> finished before the SCSI module is about to be unloaded. Currently,
> the code uses flush_scheduled_work() for this, which is going away
> because the latency can grow arbitrarily large and the behavior is
> dependent on completely unrelated work items. So, either we need to
> add a separate flush interface for ew's, flush the work item inside
> ew's or schedule them to a dedicated workqueue.
Depends what you're doing about the flush problem. The synchronisation
is inherent in the use (we're holding a reference to the module within
the executed code). The flush is to try to speed things up so the user
doesn't get annoyed during rmmod. We don't need a sync, just an
accelerator.
> >> So, unless there's a compelling reason, let's remove it.
> >
> > The open coding of if (in_atomic()) { do workqueue stuff } else
> > { execute function } is rather bug prone (most people tend to do
> > in_interrupt()). It's better to encapsulate it in an API.
>
> Compelling reason for it to exist. Why not just use work when you
> need execution context and the caller might or might not have one?
Because it's completely lame to have user context and not use it.
> > It was in SCSI ... I got told to make it generic.
>
> Heh, yeah, that would feel quite silly. Sorry about that. :-)
>
> But, really, let's just remove it. At this point, we either need to
> fortify the interface or remove it and given the current usage, I
> think we're better off with the latter.
I really don't think the open coding is a good idea. It's complex and
error prone; exactly the type of thing that should be in an API.
> If any pressing need arises,
> we can always add a proper API with all the necessary bells and
> whistles later.
James
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