linux-kernel - Re: [PATCH] mm/migrate: Mark unmap_and_move() "noinline" to avoid ICE in gcc 4.7.3

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Message-ID: <7hwq1v4iq4.fsf@deeprootsystems.com>
Date:	Wed, 01 Apr 2015 14:54:59 -0700
From:	Kevin Hilman <khilman@...nel.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Marc Zyngier <marc.zyngier@....com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Will Deacon <Will.Deacon@....com>,
	Simon Horman <horms@...ge.net.au>,
	Tyler Baker <tyler.baker@...aro.org>,
	Nishanth Menon <nm@...com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-sh\@vger.kernel.org" <linux-sh@...r.kernel.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Magnus Damm <magnus.damm@...il.com>,
	"grygorii.strashko\@linaro.org" <grygorii.strashko@...aro.org>,
	"linux-omap\@vger.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-arm-kernel\@lists.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linux Kernel Development <linux-kernel@...r.kernel.org>,
	"linux-mm\@kvack.org" <linux-mm@...ck.org>
Subject: Re: [PATCH] mm/migrate: Mark unmap_and_move() "noinline" to avoid ICE in gcc 4.7.3

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.

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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