linux-kernel - Re: [PATCH] RISC-V: fix barrier() use in <vdso/processor.h>

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Date:   Tue, 17 Nov 2020 11:00:54 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Andreas Schwab <schwab@...ux-m68k.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        linux-riscv@...ts.infradead.org,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>
Subject: Re: [PATCH] RISC-V: fix barrier() use in <vdso/processor.h>

On Mon, Nov 16, 2020 at 5:40 PM Randy Dunlap <rdunlap@...radead.org> wrote:
>
> riscv's <vdso/processor.h> uses barrier() so it should
> #include <asm/barrier.h> to prevent build errors.
>
> Fixes this build error:
>   CC [M]  drivers/net/ethernet/emulex/benet/be_main.o
> In file included from ./include/vdso/processor.h:10,
>                  from ./arch/riscv/include/asm/processor.h:11,
>                  from ./include/linux/prefetch.h:15,
>                  from drivers/net/ethernet/emulex/benet/be_main.c:14:
> ./arch/riscv/include/asm/vdso/processor.h: In function 'cpu_relax':
> ./arch/riscv/include/asm/vdso/processor.h:14:2: error: implicit declaration of function 'barrier' [-Werror=implicit-function-declaration]
>    14 |  barrier();
>
> This happens with a total of 5 networking drivers -- they all use
> <linux/prefetch.h>.
>
> rv64 allmodconfig now builds cleanly after this patch.
>
> Fixes fallout from:
> 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually exclusive")
>
> Fixes: ad5d1122b82f ("riscv: use vDSO common flow to reduce the latency of the time-related functions")

Hi Randy,
Thanks for the patch, it looks good to me.  I only had a question on
the commit message.

Is this also related to:
commit 3347acc6fcd4 ("compiler.h: fix barrier_data() on clang")

I plan to backport 3347acc6fcd4, so it would be good if all of the
follow ups are all tagged accordingly with fixes tags, so that I don't
break anything backporting 3347acc6fcd4 because I forgot or missed any
follow ups that also needed to be backported.

> Reported-by: Andreas Schwab <schwab@...ux-m68k.org>
> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Stephen Rothwell <sfr@...b.auug.org.au>
> Cc: Arvind Sankar <nivedita@...m.mit.edu>
> Cc: linux-riscv@...ts.infradead.org
> Cc: clang-built-linux@...glegroups.com
> Cc: Nick Desaulniers <ndesaulniers@...gle.com>
> Cc: Nathan Chancellor <natechancellor@...il.com>
> Cc: Paul Walmsley <paul.walmsley@...ive.com>
> Cc: Palmer Dabbelt <palmer@...belt.com>
> Cc: Albert Ou <aou@...s.berkeley.edu>
> ---
>  arch/riscv/include/asm/vdso/processor.h |    2 ++
>  1 file changed, 2 insertions(+)
>
> --- lnx-510-rc4.orig/arch/riscv/include/asm/vdso/processor.h
> +++ lnx-510-rc4/arch/riscv/include/asm/vdso/processor.h
> @@ -4,6 +4,8 @@
>
>  #ifndef __ASSEMBLY__
>
> +#include <asm/barrier.h>
> +
>  static inline void cpu_relax(void)
>  {
>  #ifdef __riscv_muldiv



-- 
Thanks,
~Nick Desaulniers