ARM: Build failures with CONFIG_HAVE_RCU_TABLE_FREE=y on linux-next

[linux@armlinux.org.uk (Russell King - ARM Linux)]

See "arm: asm/tlb.h: Fix build error implicit func declaration" on
lakml.

On Fri, Jul 27, 2018 at 11:12:35AM +0530, Keerthy wrote:
> Hi Russell,
> 
> commit 2ff6ddf19c0ec40633bd14d8fe28a289816bd98d
> Author: Rik van Riel <riel@surriel.com>
> Date:   Mon Jul 16 15:03:32 2018 -0400
> 
> x86/mm/tlb: Leave lazy TLB mode at page table free time
> 
> On linux-next introduces tlb_flush_remove_tables_local and
> tlb_flush_remove_tables functions that are more or less for x86 only.
> 
> I see build failures for standalone dra7 K2 defconfigs and NOT in case
> of omap2plus_defconfig, reason being CONFIG_HAVE_RCU_TABLE_FREE is
> defined for the failing defconfigs.
> 
> I looked at arch/arm/Kconfig which has:
> 
> select HAVE_RCU_TABLE_FREE if (SMP && ARM_LPAE)
> 
> So in case of K2G/Keystone/dra7 both SMP and LPAE are defined and hence
> CONFIG_HAVE_RCU_TABLE_FREE is defined which gives me the following build
> errors:
> 
> ti_sdk_dra7x_release_defconfig
> + make -j16 ARCH=arm
> O=/home/lcpdbld/jenkins_ws/workspace/linux_next_compile/build_out/kernel/ti_s
> dk_dra7x_release_defconfig
> <stdin>:1332:2: warning: #warning syscall io_pgetevents not implemented
> [-Wcpp]
> <stdin>:1338:2: warning: #warning syscall open_tree not implemented [-Wcpp]
> <stdin>:1341:2: warning: #warning syscall move_mount not implemented [-Wcpp]
> <stdin>:1344:2: warning: #warning syscall fsopen not implemented [-Wcpp]
> <stdin>:1347:2: warning: #warning syscall fsmount not implemented [-Wcpp]
> <stdin>:1350:2: warning: #warning syscall fspick not implemented [-Wcpp]
> <stdin>:1353:2: warning: #warning syscall fsinfo not implemented [-Wcpp]
> /scratch/lcpdbld/jenkins_ws/workspace/linux_next_compile/linux-
> kernel/mm/memory.c: In function ?tlb_remove_table_smp_sync?:
> /scratch/lcpdbld/jenkins_ws/workspace/linux_next_compile/linux-
> kernel/mm/memory.c:339:2: error: implicit declaration of function
> ?tlb_flush_remove_tables_local?; did you mean ?tlb_remove_table?? [-
> Werror=implicit-function-declaration]
>   tlb_flush_remove_tables_local(mm);
>   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   tlb_remove_table
> /scratch/lcpdbld/jenkins_ws/workspace/linux_next_compile/linux-
> kernel/mm/memory.c: In function ?tlb_table_flush?:
> /scratch/lcpdbld/jenkins_ws/workspace/linux_next_compile/linux-
> kernel/mm/memory.c:372:2: error: implicit declaration of function
> ?tlb_flush_remove_tables?; did you mean ?tlb_remove_table??
> [-Werror=implicit-
> function-declaration]
>   tlb_flush_remove_tables(tlb->mm);
>   ^~~~~~~~~~~~~~~~~~~~~~~
>   tlb_remove_table
> cc1: some warnings being treated as errors
> make[2]: *** [mm/memory.o] Error 1
> make[2]: *** Waiting for unfinished jobs....
> make[1]: *** [mm] Error 2
> make[1]: *** Waiting for unfinished jobs....
> make: *** [sub-make] Error 2
> 
> I could fix the above errors with the hunk below:
> 
> diff --git a/arch/arm/include/asm/tlb.h b/arch/arm/include/asm/tlb.h
> index d5562f9..638f2c4 100644
> --- a/arch/arm/include/asm/tlb.h
> +++ b/arch/arm/include/asm/tlb.h
> @@ -35,6 +35,15 @@
> 
>  #define MMU_GATHER_BUNDLE      8
> 
> +/*
> + * Used to flush the TLB when page tables are removed, when lazy
> + * TLB mode may cause a CPU to retain intermediate translations
> + * pointing to about-to-be-freed page table memory.
> + */
> +#ifndef HAVE_TLB_FLUSH_REMOVE_TABLES
> +#define tlb_flush_remove_tables(mm) do {} while (0)
> +#define tlb_flush_remove_tables_local(mm) do {} while (0)
> +#endif
> 
> I am sure there is a better way to fix this. Let me know if this can be
> fixed in a better way.
> 
> Regards,
> Keerthy

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