linux-kernel - [090/205] genirq: Deal with desc->set

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Message-Id: <20100730175141.815256382@clark.site>
Date:	Fri, 30 Jul 2010 10:51:47 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Thomas Gleixner <tglx@...utronix.de>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linuxppc-dev <linuxppc-dev@...abs.org>
Subject: [090/205] genirq: Deal with desc->set_type() changing desc->chip

2.6.34-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Thomas Gleixner <tglx@...utronix.de>

commit 4673247562e39a17e09440fa1400819522ccd446 upstream.

The set_type() function can change the chip implementation when the
trigger mode changes. That might result in using an non-initialized
irq chip when called from __setup_irq() or when called via
set_irq_type() on an already enabled irq.

The set_irq_type() function should not be called on an enabled irq,
but because we forgot to put a check into it, we have a bunch of users
which grew the habit of doing that and it never blew up as the
function is serialized via desc->lock against all users of desc->chip
and they never hit the non-initialized irq chip issue.

The easy fix for the __setup_irq() issue would be to move the
irq_chip_set_defaults(desc->chip) call after the trigger setting to
make sure that a chip change is covered.

But as we have already users, which do the type setting after
request_irq(), the safe fix for now is to call irq_chip_set_defaults()
from __irq_set_trigger() when desc->set_type() changed the irq chip.

It needs a deeper analysis whether we should refuse to change the chip
on an already enabled irq, but that'd be a large scale change to fix
all the existing users. So that's neither stable nor 2.6.35 material.

Reported-by: Esben Haabendal <eha@...edevelopment.dk>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: linuxppc-dev <linuxppc-dev@...abs.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 kernel/irq/manage.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -440,6 +440,9 @@ int __irq_set_trigger(struct irq_desc *d
 		/* note that IRQF_TRIGGER_MASK == IRQ_TYPE_SENSE_MASK */
 		desc->status &= ~(IRQ_LEVEL | IRQ_TYPE_SENSE_MASK);
 		desc->status |= flags;
+
+		if (chip != desc->chip)
+			irq_chip_set_defaults(desc->chip);
 	}

 	return ret;

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