linux-kernel - Re: [PATCH PREEMPT_RT]: On AT91 ARM: GPIO Interrupt handling can/will stall forever

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Message-Id: <1196178834.23808.11.camel@imap.mvista.com>
Date:	Tue, 27 Nov 2007 07:53:54 -0800
From:	Daniel Walker <dwalker@...sta.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	ARM Linux Mailing List 
	<linux-arm-kernel@...ts.arm.linux.org.uk>,
	RT <linux-rt-users@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Remy Bohmer <linux@...mer.net>
Subject: Re: [PATCH PREEMPT_RT]: On AT91 ARM: GPIO Interrupt handling
	can/will stall forever

On Tue, 2007-11-27 at 07:25 -0800, Daniel Walker wrote:
> On Tue, 2007-11-27 at 10:11 -0500, Steven Rostedt wrote:
> > Thomas,
> > 
> > Can you ACK or NACK this patch.  I know you play with a bunch of
> > hardware that this patch may affect.
> > 
> 
> My two cents, I think it's needed (or something like it).. It looks like
> handle_simple_irq normally expects a custom cascade type handler to
> unmask on return. When you switch to a threaded handler the cascade
> handler is gone and can't unmask..

I take this back .. The comment at the top of handle_simple_irq() is,

 *      Note: The caller is expected to handle the ack, clear, mask and
 *      unmask issues if necessary.


So we shouldn't need any flow control unless there is some other
factors.. 

Additionally, we have a patch in the real time tree called
"irq-mask-fix.patch" which adds an "unmask" to handle_simple_irq, but as
the note says we don't need flow control..

Daniel

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