On Tue, Aug 23, 2011 at 1:57 AM, Alan Cox [off-list ref] wrote:

On Mon, 22 Aug 2011 23:10:21 -0600 (MDT)
Paul Walmsley [off-list ref] wrote:

quoted

Convert the omap-serial hardirq handler to a threaded IRQ handler. Without
this patch, OMAP boards which use the on-board OMAP UARTs and the
omap-serial driver will not boot to userspace after commit
f3637a5f2e2eb391ff5757bc83fb5de8f9726464 ("irq: Always set IRQF_ONESHOT if
no primary handler is specified").  Enabling CONFIG_DEBUG_SHIRQ reveals
'IRQ handler type mismatch' errors:

There are multiple other drivers reporting all these problems - the
faulty irq change should be reverted at this point not the drivers
fiddled with.

Agreed. It's too late to try to fix random drivers.

The real issue seems to be that clue:

    "Enabling CONFIG_DEBUG_SHIRQ reveals 'IRQ handler type mismatch' errors"

iow, we have a shared irq, and forcing the IRQF_ONESHOT bit is
resulting in those shared interrupts now having different values of
IRQF_ONESHOT, so this test triggers:

                /*
                 * Can't share interrupts unless both agree to and are
                 * the same type (level, edge, polarity). So both flag
                 * fields must have IRQF_SHARED set and the bits which
                 * set the trigger type must match. Also all must
                 * agree on ONESHOT.
                 */
                if (!((old->flags & new->flags) & IRQF_SHARED) ||
                    ((old->flags ^ new->flags) & IRQF_TRIGGER_MASK) ||
                    ((old->flags ^ new->flags) & IRQF_ONESHOT)) {
                        old_name = old->name;
                        goto mismatch;
                }

and the irq isn't installed at all (setup_irq returns with EBUSY).

So the commit that caused this problem was simply bogus. The commit log says

                       "Since it is required for those users and
    there is no difference for others it makes sense to add this flag
    unconditionally."

but the "there is no difference for others" seems to be total crap,
exactly because it results in this IRQF mismatch.

So I think that commit should just be reverted. Thomas?

                           Linus
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