Re: [PATCH] powerpc pseries eeh: Convert to kthread API

On Mon, 2007-04-23 at 20:08 -0600, Eric W. Biederman wrote:

Benjamin Herrenschmidt [off-list ref] writes:

quoted

quoted

The only reason for using threads here is to get the error recovery
out of an interrupt context (where errors may be detected), and then,
an hour later, decrement a counter (which is how we limit these to 
6 per hour). Thread reaping is "trivial", the thread just exits
after an hour.

In addition, it should be a thread and not done from within keventd
because :

 - It can take a long time (well, relatively but still too long for a
work queue)

 - The driver callbacks might need to use keventd or do flush_workqueue
to synchronize with their own workqueues when doing an internal
recovery.

quoted

Since these are events rare, I've no particular concern about
performance or resource consumption. The current code seems 
to work just fine. :-)

I think moving to kthread's is cleaner (just a wrapper around kernel
threads that simplify dealing with reaping them out mostly) and I agree
with Christoph that it would be nice to be able to "fire off" kthreads
from interrupt context.. in many cases, we abuse work queues for things
that should really done from kthreads instead (basically anything that
takes more than a couple hundred microsecs or so).

On that note does anyone have a problem is we manage the irq spawning
safe kthreads the same way that we manage the work queue entries.

i.e. by a structure allocated by the caller?

Not sure... I can see places where I might want to spawn an arbitrary
number of these without having to preallocate structures... and if I
allocate on the fly, then I need a way to free that structure when the
kthread is reaped which I don't think we have currently, do we ? (In
fact, I could use that for other things too now that I'm thinking of
it ... I might have a go at providing optional kthread destructors).

Ben.