linux-kernel - Re: Build error due to commit 458aa76d132dc ("mm/thp/migration: switch from flush_tlb_range to flush_pmd_tlb

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Message-ID: <87k2kvt7p6.fsf@linux.vnet.ibm.com>
Date:	Tue, 22 Mar 2016 10:44:45 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-snps-arc@...ts.infradead.org,
	Vineet Gupta <vgupta@...opsys.com>
Subject: Re: Build error due to commit 458aa76d132dc ("mm/thp/migration: switch from flush_tlb_range to flush_pmd_tlb_range")

Guenter Roeck <linux@...ck-us.net> writes:

> [ text/plain ]
> Hi,
>
> Your commit 458aa76d132dc1 ("mm/thp/migration: switch from flush_tlb_range
> to flush_pmd_tlb_range") causes a build error when building
> arcv2:vdk_hs38_smp_defconfig.
>
> include/asm-generic/pgtable.h:799:45: note: in expansion of macro ‘BUILD_BUG’
>  #define flush_pmd_tlb_range(vma, addr, end) BUILD_BUG()
>                                               ^
> ./arch/arc/include/asm/tlbflush.h:37:13: note:
> 	in expansion of macro ‘flush_pmd_tlb_range’
>
> The build triggers the newly introduced BUILD_BUG().
>
> When building the image without the BUILD_BUG(), ie with no definition
> of flush_pmd_tlb_range(), the problem is gone. This suggests that the
> function is not needed for this build.
>
> I could submit a patch to remove the BUILD_BUG(), but maybe you had a reason
> for introducing it. Can you elaborate why you introduced the BUILD_BUG() ?
>

Isn't this going to be fixed by an update to ARC tree ?

http://article.gmane.org/gmane.linux.kernel.mm/148412

I also don't understand why we would hit that BUILD_BUG, if we are not
calling flush_pmd_tlb_range().

-aneesh