[1/2] cxl: Keep IRQ mappings on context teardown

[Michael Ellerman]

On Fri, 2016-22-04 at 04:57:48 UTC, Michael Neuling wrote:
> Keep IRQ mappings on context teardown.  This won't leak IRQs as if we
> allocate the mapping again, the generic code will give the same
> mapping used last time.
> 
> Doing this works around a race in the generic code. Masking the
> interrupt introduces a race which can crash the kernel or result in
> IRQ that is never EOIed. The lost of EOI results in all subsequent
> mappings to the same HW IRQ never receiving an interrupt.
> 
> We've seen this race with cxl test cases which are doing heavy context
> startup and teardown at the same time as heavy interrupt load.
> 
> A fix to the generic code is being investigated also.
> 
> Signed-off-by: Michael Neuling <mikey at neuling.org>
> cc: stable at vger.kernel.org # 3.8
> Tested-by: Andrew Donnellan <andrew.donnellan at au1.ibm.com>
> Acked-by: Ian Munsie <imunsie at au1.ibm.com>
> Tested-by: Vaibhav Jain <vaibhav at linux.vnet.ibm.com>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/d6776bba44d9752f6cdf640046

cheers