linux-kernel - Re: lockdep and threaded IRQs (was: ...)

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Date:	Sat, 28 Feb 2009 21:55:13 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	David Brownell <david-b@...bell.net>
cc:	Andrew Morton <akpm@...ux-foundation.org>, me@...ipebalbi.com,
	linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
	felipe.balbi@...ia.com, dmitry.torokhov@...il.com,
	sameo@...nedhand.com, a.p.zijlstra@...llo.nl
Subject: Re: lockdep and threaded IRQs (was: ...)

On Sat, 28 Feb 2009, David Brownell wrote:
> Got a version that applies to mainline GIT?

http://tglx.de/~tglx/patches.tar.bz2 
 
> At a quick glance it looks like these patches don't cover
> set_irq_chained_handler(), which would be trouble since
> __setup_irq() doesn't get called in those cases.

Hmm, I did not think about chained handlers where the demux handler
needs to run in a thread as well. Usually demux handlers just have a
fast path kicking the particular real handlers.

> They should however handle simpler cases, like I2C devices
> that only expose one IRQ instead of needing to demux several
> dozen IRQs going to different drivers and subsystems.
> 
> And, not touching lockdep, the original ugliness will still
> be needed (re-enabling IRQs in threaded handlers).

Err ? The threaded handlers run with interrupts enabled.

static int irq_thread(void *data)
{
        ...

        while (!kthread_should_stop()) {
                set_current_state(TASK_INTERRUPTIBLE);
                if (irq_thread_should_run(action) && current->irqaction) {
                        __set_current_state(TASK_RUNNING);
                        action->handler(action->irq, action->dev_id);
                } else
                        schedule();
        }

Thanks,

	tglx
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