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

From: Randy Dunlap <rdunlap@infradead.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Andreas Schwab <schwab@linux-m68k.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	linux-riscv@lists.infradead.org,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>
Subject: Re: [PATCH] RISC-V: fix barrier() use in <vdso/processor.h>
Date: Tue, 17 Nov 2020 11:27:28 -0800	[thread overview]
Message-ID: <fe040988-c076-8dec-8268-3fbaa8b39c0f@infradead.org> (raw)
In-Reply-To: <9ab43756-6c48-c5e8-3a5d-e44bba070a97@infradead.org>

On 11/17/20 11:22 AM, Randy Dunlap wrote:
> On 11/17/20 11:00 AM, Nick Desaulniers wrote:
>> On Mon, Nov 16, 2020 at 5:40 PM Randy Dunlap <rdunlap@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")
>>
>> 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")
> 
> Hi Nick,
> Yes, it looks like I tagged the wrong commit in Fixes:
> Thanks for noticing that.
> 

I'll send a v2 with corrections.

> 
>> 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@linux-m68k.org>
>>> Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
>>> Cc: Andrew Morton <akpm@linux-foundation.org>
>>> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
>>> Cc: Arvind Sankar <nivedita@alum.mit.edu>
>>> Cc: linux-riscv@lists.infradead.org
>>> Cc: clang-built-linux@googlegroups.com
>>> Cc: Nick Desaulniers <ndesaulniers@google.com>
>>> Cc: Nathan Chancellor <natechancellor@gmail.com>
>>> Cc: Paul Walmsley <paul.walmsley@sifive.com>
>>> Cc: Palmer Dabbelt <palmer@dabbelt.com>
>>> Cc: Albert Ou <aou@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

-- 
~Randy