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

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Message-ID: <m1ejmav80l.fsf@ebiederm.dsl.xmission.com>
Date:	Mon, 23 Apr 2007 20:08:42 -0600
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Linas Vepstas <linas@...tin.ibm.com>,
	Christoph Hellwig <hch@...radead.org>,
	"<Andrew Morton" <akpm@...l.org>, containers@...ts.osdl.org,
	Oleg Nesterov <oleg@...sign.ru>, linux-kernel@...r.kernel.org,
	Paul Mackerras <paulus@...ba.org>, linux-s390@...r.kernel.org,
	linuxppc-dev@...abs.org
Subject: Re: [PATCH] powerpc pseries eeh: Convert to kthread API

Benjamin Herrenschmidt <benh@...nel.crashing.org> writes:

>> 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.
>
>> 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?

Eric
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