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SubjectRe: [PATCH 2/3] work_on_cpu: Use our own workqueue.
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On Thursday 05 February 2009 02:06:36 Andrew Morton wrote:
> On Wed, 4 Feb 2009 21:11:35 +1030 Rusty Russell <rusty@rustcorp.com.au> wrote:
>
> > On Wednesday 04 February 2009 13:31:11 Andrew Morton wrote:
> > > On Wed, 4 Feb 2009 13:14:31 +1030 Rusty Russell <rusty@rustcorp.com.au> wrote:
> > > > I think you're right though: smp_call_function_single (or neat wrappers)
> > > > where possible, work_on_cpu which can fail for the others, and we'll just
> > > > have to plumb in the error returns.
> > >
> > > I bet a lot of those can use plain old schedule_work_on().
> >
> > Which is where work_on_cpu started: a little wrapper around schedule_work_on.
> >
> > We're going in circles, no?
>
> No, we've made some progress. We have a better understanding of what
> the restrictions, shortcomings and traps are in this stuff. We've
> learned (surprise!) that a one-size-fits-all big hammer wasn't such a
> great idea.
>
> Proposed schedule_work_on() rule: either the flush_work() caller or the
> callback should not hold any explicit or implicit sleeping locks.

But as you found out looking through these, it's really hard to tell. I can
guess, but that's a little fraught...

How about we make work_on_cpu spawn a temp thread; if you care, use
something cleverer? Spawning a thread just isn't that slow.

Meanwhile, I'll prepare patches to convert all the non-controversial cases
(ie. smp_call_function-style ones).

Cheers,
Rusty.


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