linux-kernel - Re: linux-next: workqueues tree build failure

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Date:	Fri, 27 Nov 2009 09:37:36 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Tejun Heo <tj@...nel.org>
Cc:	Andy Walls <awalls@...ix.net>,
	Peter Ujfalusi <peter.ujfalusi@...ia.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	"linux-next@...r.kernel.org" <linux-next@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Subject: Re: linux-next: workqueues tree build failure

At Fri, 27 Nov 2009 11:02:25 +0900,
Tejun Heo wrote:
> 
> Hello,
> 
> 11/26/2009 09:40 PM, Andy Walls wrote:
> >> * If you need to respond fast, wouldn't you be doing that from IRQ
> >>   handler or softirq?  Do you need task context?
> > 
> > I'm not sure doing things like I2C transactions in the in the top half
> > of the IRQ handler is generally viable.  On shared IRQ lines, wouldn't
> > this hold off the interrupt for another device for too long?
> > 
> > For example, I already ran across the case of an error path in the ahci
> > disk controller driver interrupt handler holding off interrupts from the
> > cx18 driver longer than the CX23418 firmware would tolerate on a shared
> > interrupt line.
> 
> Sounds like it should be using bottom half tasklet not workqueue.
> Tasklet is exactly designed to handle situations like this.  Is there
> any reason tasklet can't be used?

Right now the h/w accessing code is using mutex.  I'm not sure whether
the deeper part might sleep, though...


Takashi
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