Patch "genirq: Deal with desc->set_type() changing desc->chip" has been added to the 2.6.32-stable tree

This is a note to let you know that I've just added the patch titled

    genirq: Deal with desc->set_type() changing desc->chip

to the 2.6.32-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
genirq-deal-with-desc-set_type-changing-desc-chip.patch
and it can be found in the queue-2.6.32 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Thomas Gleixner <[email protected]>
Date: Mon, 7 Jun 2010 17:53:51 +0200
Subject: genirq: Deal with desc->set_type() changing desc->chip

From: Thomas Gleixner <[email protected]>

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.

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

@@ -436,6 +436,9 @@ 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;

Patches currently in stable-queue which might be from [email protected] are

queue-2.6.32/genirq-deal-with-desc-set_type-changing-desc-chip.patch