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

[Palmer Dabbelt]

On Mon, 16 Nov 2020 17:39:51 PST (-0800), rdunlap at infradead.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")
> Reported-by: Andreas Schwab <schwab at linux-m68k.org>
> Signed-off-by: Randy Dunlap <rdunlap at infradead.org>
> Cc: Andrew Morton <akpm at linux-foundation.org>
> Cc: Stephen Rothwell <sfr at canb.auug.org.au>
> Cc: Arvind Sankar <nivedita at alum.mit.edu>
> Cc: linux-riscv at lists.infradead.org
> Cc: clang-built-linux at googlegroups.com
> Cc: Nick Desaulniers <ndesaulniers at google.com>
> Cc: Nathan Chancellor <natechancellor at gmail.com>
> Cc: Paul Walmsley <paul.walmsley at sifive.com>
> Cc: Palmer Dabbelt <palmer at dabbelt.com>
> Cc: Albert Ou <aou at eecs.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, this is on fixes.