Date:	Thu, 2 Apr 2015 13:12:30 -0600
From:	Lina Iyer <lina.iyer@...aro.org>
To:	Kevin Hilman <khilman@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Nishanth Menon <nm@...com>,
	Magnus Damm <magnus.damm@...il.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Marc Zyngier <marc.zyngier@....com>,
	Tyler Baker <tyler.baker@...aro.org>,
	"linux-sh@...r.kernel.org" <linux-sh@...r.kernel.org>,
	Will Deacon <Will.Deacon@....com>,
	Linux Kernel Development <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Simon Horman <horms@...ge.net.au>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"grygorii.strashko@...aro.org" <grygorii.strashko@...aro.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] mm/migrate: Mark unmap_and_move() "noinline" to avoid
 ICE in gcc 4.7.3

On Wed, Apr 01 2015 at 15:57 -0600, Kevin Hilman wrote:
>Andrew Morton <akpm@...ux-foundation.org> writes:
>
>> On Wed, 01 Apr 2015 10:47:49 +0100 Marc Zyngier <marc.zyngier@....com> wrote:
>>
>>> > -static int unmap_and_move(new_page_t get_new_page, free_page_t put_new_page,
>>> > -			unsigned long private, struct page *page, int force,
>>> > -			enum migrate_mode mode)
>>> > +static noinline int unmap_and_move(new_page_t get_new_page,
>>> > +				   free_page_t put_new_page,
>>> > +				   unsigned long private, struct page *page,
>>> > +				   int force, enum migrate_mode mode)
>>> >  {
>>> >  	int rc = 0;
>>> >  	int *result = NULL;
>>> >
>>>
>>> Ouch. That's really ugly. And on 32bit ARM, we end-up spilling half of
>>> the parameters on the stack, which is not going to help performance
>>> either (not that this would be useful on 32bit ARM anyway...).
>>>
>>> Any chance you could make this dependent on some compiler detection
>>> mechanism?
>>
>> With my arm compiler (gcc-4.4.4) the patch makes no difference -
>> unmap_and_move() isn't being inlined anyway.
>>
>> How does this look?
>>
>> Kevin, could you please retest?  I might have fat-fingered something...
>
>Your patch on top of Geert's still compiles fine for me with gcc-4.7.3.
>However, I'm not sure how specific we can be on the versions.
>
>/me goes to test a few more compilers...   OK...
>
>ICE: 4.7.1, 4.7.3, 4.8.3
>OK: 4.6.3, 4.9.2, 4.9.3
>
>The diff below[2] on top of yours compiles fine here and at least covers
>the compilers I *know* to trigger the ICE.

I see ICE on 
arm-linux-gnueabi-gcc (Ubuntu/Linaro 4.7.4-2ubuntu1) 4.7.4

>
>Kevin
>
>
>[1]
>diff --git a/mm/migrate.c b/mm/migrate.c
>index 25fd7f6291de..6e15ae3248e0 100644
>--- a/mm/migrate.c
>+++ b/mm/migrate.c
>@@ -901,10 +901,10 @@ out:
> }
>
> /*
>- * gcc-4.7.3 on arm gets an ICE when inlining unmap_and_move().  Work around
>+ * gcc 4.7 and 4.8 on arm gets an ICE when inlining unmap_and_move().  Work around
>  * it.
>  */
>-#if GCC_VERSION == 40703 && defined(CONFIG_ARM)
>+#if (GCC_VERSION >= 40700 && GCC_VERSION < 40900) && defined(CONFIG_ARM)
> #define ICE_noinline noinline
> #else
> #define ICE_noinline
>
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