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Subject: Re: [PATCH v2] powerpc/prom_init: add __init markers to all functions
To:     Masahiro Yamada <yamada.masahiro@socionext.com>,
        linux-kbuild@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        Michael Ellerman <mpe@ellerman.id.au>
Cc:     Mathieu Malaterre <malat@debian.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        linux-kernel@vger.kernel.org, Paul Mackerras <paulus@samba.org>
References: <1550641996-21937-1-git-send-email-yamada.masahiro@socionext.com>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <cc7ebb9b-90ac-e1ea-5057-cfcae6e772b8@c-s.fr>
Date:   Wed, 20 Feb 2019 07:54:00 +0100
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Le 20/02/2019 à 06:53, Masahiro Yamada a écrit :
> It is fragile to rely on the compiler's optimization to avoid the
> section mismatch. Some functions may not be necessarily inlined
> when the compiler's inlining heuristic changes.
> 
> Add __init markers consistently.
> 
> As for prom_getprop() and prom_getproplen(), they are marked as
> 'inline', so inlining is guaranteed because PowerPC never enables
> CONFIG_OPTIMIZE_INLINING. However, it would be better to leave the
> inlining decision to the compiler. I replaced 'inline' with __init.
> I added __maybe_unused to prom_getproplen() because it is currently
> relying on the side-effect of 'inline'; GCC does not report
> -Wunused-function warnings for functions with 'inline' marker.

__maybe_unused is really a bad trick that should be avoided, as it hides 
unused functions.

Why is it a problem to keep prom_getproplen() as 'static inline' ? Most 
small helpers are defined that way. Usually they are in an included 
header file, but what's really the problem with having it here directly ?

Christophe

> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
> 
> Changes in v2:
>    - Add __maybe_unsed to prom_getproplen()
>    - Add __init to enter_prom() as well
> 
>   arch/powerpc/kernel/prom_init.c | 29 +++++++++++++++--------------
>   1 file changed, 15 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
> index f33ff41..1bad0ac 100644
> --- a/arch/powerpc/kernel/prom_init.c
> +++ b/arch/powerpc/kernel/prom_init.c
> @@ -138,9 +138,9 @@ extern void __start(unsigned long r3, unsigned long r4, unsigned long r5,
>   		    unsigned long r9);
>   
>   #ifdef CONFIG_PPC64
> -extern int enter_prom(struct prom_args *args, unsigned long entry);
> +extern int __init enter_prom(struct prom_args *args, unsigned long entry);
>   #else
> -static inline int enter_prom(struct prom_args *args, unsigned long entry)
> +static int __init enter_prom(struct prom_args *args, unsigned long entry)
>   {
>   	return ((int (*)(struct prom_args *))entry)(args);
>   }
> @@ -501,19 +501,20 @@ static int __init prom_next_node(phandle *nodep)
>   	}
>   }
>   
> -static inline int prom_getprop(phandle node, const char *pname,
> +static int __init prom_getprop(phandle node, const char *pname,
>   			       void *value, size_t valuelen)
>   {
>   	return call_prom("getprop", 4, 1, node, ADDR(pname),
>   			 (u32)(unsigned long) value, (u32) valuelen);
>   }
>   
> -static inline int prom_getproplen(phandle node, const char *pname)
> +static int __init __maybe_unused prom_getproplen(phandle node,
> +						 const char *pname)
>   {
>   	return call_prom("getproplen", 2, 1, node, ADDR(pname));
>   }
>   
> -static void add_string(char **str, const char *q)
> +static void __init add_string(char **str, const char *q)
>   {
>   	char *p = *str;
>   
> @@ -523,7 +524,7 @@ static void add_string(char **str, const char *q)
>   	*str = p;
>   }
>   
> -static char *tohex(unsigned int x)
> +static char __init *tohex(unsigned int x)
>   {
>   	static const char digits[] __initconst = "0123456789abcdef";
>   	static char result[9] __prombss;
> @@ -570,7 +571,7 @@ static int __init prom_setprop(phandle node, const char *nodename,
>   #define islower(c)	('a' <= (c) && (c) <= 'z')
>   #define toupper(c)	(islower(c) ? ((c) - 'a' + 'A') : (c))
>   
> -static unsigned long prom_strtoul(const char *cp, const char **endp)
> +static unsigned long __init prom_strtoul(const char *cp, const char **endp)
>   {
>   	unsigned long result = 0, base = 10, value;
>   
> @@ -595,7 +596,7 @@ static unsigned long prom_strtoul(const char *cp, const char **endp)
>   	return result;
>   }
>   
> -static unsigned long prom_memparse(const char *ptr, const char **retptr)
> +static unsigned long __init prom_memparse(const char *ptr, const char **retptr)
>   {
>   	unsigned long ret = prom_strtoul(ptr, retptr);
>   	int shift = 0;
> @@ -2924,7 +2925,7 @@ static void __init fixup_device_tree_pasemi(void)
>   	prom_setprop(iob, name, "device_type", "isa", sizeof("isa"));
>   }
>   #else	/* !CONFIG_PPC_PASEMI_NEMO */
> -static inline void fixup_device_tree_pasemi(void) { }
> +static void __init fixup_device_tree_pasemi(void) { }
>   #endif
>   
>   static void __init fixup_device_tree(void)
> @@ -2986,15 +2987,15 @@ static void __init prom_check_initrd(unsigned long r3, unsigned long r4)
>   
>   #ifdef CONFIG_PPC64
>   #ifdef CONFIG_RELOCATABLE
> -static void reloc_toc(void)
> +static void __init reloc_toc(void)
>   {
>   }
>   
> -static void unreloc_toc(void)
> +static void __init unreloc_toc(void)
>   {
>   }
>   #else
> -static void __reloc_toc(unsigned long offset, unsigned long nr_entries)
> +static void __init __reloc_toc(unsigned long offset, unsigned long nr_entries)
>   {
>   	unsigned long i;
>   	unsigned long *toc_entry;
> @@ -3008,7 +3009,7 @@ static void __reloc_toc(unsigned long offset, unsigned long nr_entries)
>   	}
>   }
>   
> -static void reloc_toc(void)
> +static void __init reloc_toc(void)
>   {
>   	unsigned long offset = reloc_offset();
>   	unsigned long nr_entries =
> @@ -3019,7 +3020,7 @@ static void reloc_toc(void)
>   	mb();
>   }
>   
> -static void unreloc_toc(void)
> +static void __init unreloc_toc(void)
>   {
>   	unsigned long offset = reloc_offset();
>   	unsigned long nr_entries =
>