Subject: Re: [V3] powerpc/irq: Enable some more exceptions in /proc/interrupts interface

From: Michael Ellerman <[email-masked]>
Date: Fri, 14 Aug 2015 12:52:29 +1000

On Thu, 2015-08-06 at 18:54 +0530, Anshuman Khandual wrote:
> On 08/04/2015 03:27 PM, Michael Ellerman wrote:
> > On Mon, 2015-13-07 at 08:16:06 UTC, Anshuman Khandual wrote:
> >> This patch enables facility unavailable exceptions for generic facility,
> >> FPU, ALTIVEC and VSX in /proc/interrupts listing by incrementing their
> >> newly added IRQ statistical counters as and when these exceptions happen.
> >> This also adds couple of helper functions which will be called from within
> >> the interrupt handler context to update their statistics. Similarly this
> >> patch also enables alignment and program check exceptions as well.
> > 
> > ...
> > 
> >> diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
> >> index 0a0399c2..a86180c 100644
> >> --- a/arch/powerpc/kernel/exceptions-64s.S
> >> +++ b/arch/powerpc/kernel/exceptions-64s.S
> >> @@ -1158,6 +1158,7 @@ BEGIN_FTR_SECTION
> >>  END_FTR_SECTION_IFSET(CPU_FTR_TM)
> >>  #endif
> >>  	bl	load_up_fpu
> >> +	bl	fpu_unav_exceptions_count
> > 
> > Is it safe to call C code here?
> 
> Hmm, is it not ? I had that question but was not really sure. Dont
> understand the difference between 'fast_exception_return' and
> 'ret_from_except' completely.

If you're "not really sure" it's correct, please say so in the change log!

I'd rather you didn't send me patches with possibly subtle bugs in core code.

cheers