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

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Message-ID: <20201117193202.GA1574448@rani.riverdale.lan>
Date:   Tue, 17 Nov 2020 14:32:02 -0500
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        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 Tue, Nov 17, 2020 at 11:22:39AM -0800, 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@...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")
> 
> Hi Nick,
> Yes, it looks like I tagged the wrong commit in Fixes:
> Thanks for noticing that.
> 

Thanks for the patch!

Acked-by: Arvind Sankar <nivedita@...m.mit.edu>

Generally speaking, should compiler_types.h be considered "internal"?
i.e. everyone should include compiler.h, not compiler_types.h directly?

Eg for another potential case that might bite is that RELOC_HIDE is
defined in compiler_types.h, except for clang, which will only have a
definition if compiler.h is included.