On 14/06/12 08:30, Andrew Morton wrote:

On Thu, 14 Jun 2012 08:14:49 +0100 Lee Jones[off-list ref]  wrote:

quoted

On 13/06/12 23:25, Andrew Morton wrote:

quoted

On Tue, 12 Jun 2012 09:57:37 +0100
Lee Jones[off-list ref]   wrote:

quoted

The kernel now forces IRQs to be ONESHOT if no IRQ handler is passed.

What does this mean.  The kernel crashes?  The registration fails?  A
warning is emitted?

When fixing a bug, please fully describe the consequences of that bug.

quoted

Cc: stable at vger.kernel.org

Especially when suggesting a -stable backport.

No problem. I'll try to remember that for next time.

I see that you've taken the patch into your tree however. So do you want
me to update the commit log and resubmit, or are you going to 'let this
one slide'?

Please read my emails - they're very nice!  "What does this mean.  The
kernel crashes?  The registration fails?  A warning is emitted?".  You
answer that, I copy-n-paste into changelog and we're done.

Ah, you're a star!

Registration fails:

__setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
{

<snip>

	if (new->flags & IRQF_ONESHOT) {

<snip>

	} else if (new->handler == irq_default_primary_handler) {
		/*
		 * The interrupt was requested with handler = NULL, so
		 * we use the default primary handler for it. But it
		 * does not have the oneshot flag set. In combination
		 * with level interrupts this is deadly, because the
		 * default primary handler just wakes the thread, then
		 * the irq lines is reenabled, but the device still
		 * has the level irq asserted. Rinse and repeat....
		 *
		 * While this works for edge type interrupts, we play
		 * it safe and reject unconditionally because we can't
		 * say for sure which type this interrupt really
		 * has. The type flags are unreliable as the
		 * underlying chip implementation can override them.
		 */
		pr_err("Threaded irq requested with handler=NULL and !ONESHOT for irq %d\n", irq);
		ret = -EINVAL;
		goto out_mask;
	}

<snip>

-- 
Lee Jones
Linaro ST-Ericsson Landing Team Lead
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