linux-kernel - Re: [RFC PATCH] hrtimer: removing all ur callback modes

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Message-Id: <1228810331.12729.59.camel@twins>
Date:	Tue, 09 Dec 2008 09:12:11 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oliver Hartkopp <oliver@...tkopp.net>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [RFC PATCH] hrtimer: removing all ur callback modes

On Tue, 2008-12-09 at 09:07 +0100, Oliver Hartkopp wrote:

> I wouldn't be that sure that all the other sites can cope with it as i 
> only detected the problems with my code under heavy load ...

Most other sites only fiddle some bits and do a wakeup of some task or
other - they usually already did spin_lock_irqsave() to protect the
state they poked at.

But sure, testing is always the best way.

> >> Any idea?
> >>     
> >
> > What are the timing constraints of your problem? - I assume they are not
> > too aggressive, otherwise you'd not be able to run from softirq, could
> > you run from keventd?
> >   
> 
> I browsed some code that's using hrtimers and found some hopefully good 
> example in drivers/s390/crypto/ap_bus.c : They are using the hrtimer to 
> schedule a tasklet which is running in soft-irq context:
> 
> http://lxr.linux.no/linux+v2.6.27.8/drivers/s390/crypto/ap_bus.c#L1150
> 
> This could also be the correct approach for my sock_queue_rcv_skb() 
> problem, right?

In as far as tasklets are correct, yes, that would work for you too.

> Regards,
> Oliver
> 
> ps. What is the intended release for this hrtimer cleanup? 2.6.29?

I think so, Thomas, Ingo?
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