linux-kernel - Re: test for "spurious" IRQ ignores possible IRQ_WAKE

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Date:	Fri, 18 Sep 2009 00:18:13 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	"Robert P. J. Day" <rpjday@...shcourse.ca>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: test for "spurious" IRQ ignores possible IRQ_WAKE_THREAD value

[Robert P. J. Day - Thu, Sep 17, 2009 at 04:08:32PM -0400]
...
| > Hi Robert,
| >
| > It could that IRQ_WAKE_THREAD is just missed here. I suppose it was
| > brough there as thread irq merged. But I think only Thomas know for
| > sure, I definitely miss something :) CC'ed
| 
|   actually, after a bit more reading, i found this in
| kernel/irq/handle.c:
|                 ...
|                 switch (ret) {
|                 case IRQ_WAKE_THREAD:
|                         /*
|                          * Set result to handled so the spurious check
|                          * does not trigger.
|                          */
|                         ret = IRQ_HANDLED;
|                         ...
| 
| so it looks like that value of IRQ_WAKE_THREAD is simply "mapped" to
| IRQ_HANDLED, and perhaps that's done before __report_bad_irq is ever
| called so that that latter routine never sees a value of
| IRQ_WAKE_THREAD.  but that's just a guess.
| 
| rday
| --

yeah, Thomas just pointed it too :) The note_interrupt is
called after handle_IRQ_event (except a few drivers which
don;t use threaded irq) so it doesnt reach bad irq state
with IRQ_WAKE_THREAD, for now at least.

	-- Cyrill
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