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

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  Can we conditionally force threading irq with primary and thread  handler? Yunhong Jiang <yunhong.jiang@linux.intel.com> - 2015-12-03 20:30 +0100
    Re: Can we conditionally force threading irq with primary and thread  handler? Thomas Gleixner <tglx@linutronix.de> - 2015-12-03 23:40 +0100
      Re: Can we conditionally force threading irq with primary and thread  handler? Yunhong Jiang <yunhong.jiang@linux.intel.com> - 2015-12-04 00:00 +0100

#1283281 — Can we conditionally force threading irq with primary and thread handler?

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

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#1283424

Yunhong,

On Thu, 3 Dec 2015, Yunhong Jiang wrote:

> 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 you want to avoid that the primary handler is force threaded, then
you can indicate that with IRQF_NO_THREAD.

Thanks,

	tglx


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#1283437

On Thu, Dec 03, 2015 at 11:33:14PM +0100, Thomas Gleixner wrote:
> Yunhong,
> 
> On Thu, 3 Dec 2015, Yunhong Jiang wrote:
> 
> > 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 you want to avoid that the primary handler is force threaded, then
> you can indicate that with IRQF_NO_THREAD.

Thaks for reply.
Sure, will do that way. Just feel a bit weird with a valid thread_fn and a 
IRQF_NO_THREAD flags.

Thanks
--jyh
> 
> Thanks,
> 
> 	tglx
> 
> 
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