Can we conditionally force threading irq with primary and thread handler?

[Yunhong Jiang <yunhong.jiang@linux.intel.com>]

Hi, Thomas
	On Commit 2a1d3ab8986d1b2 ("genirq: Handle force threading of irqs 
with primary and thread handler"), even if the caller of 
request_threaded_irq() provides a primary handler, that primary handler will 
be invoked in thread context. This may cause some latency issue for high 
real time requirement.

	I checked the discussion on https://lkml.org/lkml/2015/9/19/372 with 
Okuno and seems we need this change only if the irq is shared, otherwise, we 
can still use Okuno's mechanism, am I right? Do you think it's ok to force 
the primary handler for shared IRQ, otherwise, clear the IRQF_ONESHOT?

	If yes, I will cook a patch for it.

Thanks
--jyh