linux-kernel - [PATCH] x86/time: Correct the attribute on jiffies' definition

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Message-Id: <20181013005311.28617-1-natechancellor@gmail.com>
Date:   Fri, 12 Oct 2018 17:53:12 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>
Cc:     "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>
Subject: [PATCH] x86/time: Correct the attribute on jiffies' definition

Clang warns that the declaration of jiffies in include/linux/jiffies.h
doesn't match the definition in arch/x86/time/kernel.c:

arch/x86/kernel/time.c:29:42: warning: section does not match previous declaration [-Wsection]
__visible volatile unsigned long jiffies __cacheline_aligned = INITIAL_JIFFIES;
                                         ^
./include/linux/cache.h:49:4: note: expanded from macro '__cacheline_aligned'
                 __section__(".data..cacheline_aligned")))
                 ^
./include/linux/jiffies.h:81:31: note: previous attribute is here
extern unsigned long volatile __cacheline_aligned_in_smp __jiffy_arch_data jiffies;
                              ^
./arch/x86/include/asm/cache.h:20:2: note: expanded from macro '__cacheline_aligned_in_smp'
        __page_aligned_data
        ^
./include/linux/linkage.h:39:29: note: expanded from macro '__page_aligned_data'
#define __page_aligned_data     __section(.data..page_aligned) __aligned(PAGE_SIZE)
                                ^
./include/linux/compiler_attributes.h:233:56: note: expanded from macro '__section'
#define __section(S)                    __attribute__((__section__(#S)))
                                                       ^
1 warning generated.

The declaration was changed in commit 7c30f352c852 ("jiffies.h: declare
jiffies and jiffies_64 with ____cacheline_aligned_in_smp") but wasn't
updated here. Make them match so Clang no longer warns.

Link: https://github.com/ClangBuiltLinux/linux/issues/98
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
---
 arch/x86/kernel/time.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/time.c b/arch/x86/kernel/time.c
index b23f5420b26a..0e14f6c0d35e 100644
--- a/arch/x86/kernel/time.c
+++ b/arch/x86/kernel/time.c
@@ -26,7 +26,7 @@
 #include <asm/time.h>
 
 #ifdef CONFIG_X86_64
-__visible volatile unsigned long jiffies __cacheline_aligned = INITIAL_JIFFIES;
+__visible volatile unsigned long jiffies __cacheline_aligned_in_smp = INITIAL_JIFFIES;
 #endif
 
 unsigned long profile_pc(struct pt_regs *regs)
-- 
2.19.1