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SubjectRe: [RFC][PATCH] create workqueue threads only when needed
On Sat, 31 Jan 2009 19:03:49 +0100
Frederic Weisbecker <> wrote:

> > one thing to look at for work queues that never get work is to see
> > if they are appropriate for the async function call interface
> > (the only requirement for that is that they need to cope with
> > calling inline in exceptional cases)
> >
> Hi Arjan,
> There is one thing that make it hard to replace workqueues in such
> cases, there is not guarantee the function will run in user context
> because of this condition:
> if (!async_enabled || !entry || atomic_read(&entry_count) > MAX_WORK)
> I wanted to replace kpsmoused with an async function but I want to
> schedule a slow work that can't be done from irq...

if there is enough value in having a variant that is guaranteed to
always run from a thread we could add that. Likely that needs that the
caller passes in a bit of memory, but that's not too big a deal.
If there is only 1 in the entire kernel it might not be worth it,
but if it's a common pattern then for sure...

do you have a feeling on how common this is ?

Arjan van de Ven Intel Open Source Technology Centre
For development, discussion and tips for power savings,

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