linux-kernel - Re: [PATCH 4/9] MIPS: MT: Remove "weak" from vpe

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Date:	Mon, 13 Jul 2015 11:27:55 +0100
From:	James Hogan <james.hogan@...tec.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Ralf Baechle <ralf@...ux-mips.org>
CC:	Andrew Bresticker <abrestic@...omium.org>,
	<linux-mips@...ux-mips.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/9] MIPS: MT: Remove "weak" from vpe_run() declaration

On 13/07/15 00:11, Bjorn Helgaas wrote:
> Weak header file declarations are error-prone because they make every
> definition weak, and the linker chooses one based on link order (see
> 10629d711ed7 ("PCI: Remove __weak annotation from pcibios_get_phb_of_node
> decl")).
> 
> That's not a problem for vpe_run() because Kconfig ensures there's never
> more than one definition:
> 
>   - vpe_run() is defined in arch/mips/kernel/vpe-mt.c if
>     CONFIG_MIPS_VPE_LOADER_MT=y
> 
>   - vpe_run() is defined in arch/mips/mti-malta/malta-amon.c if
>     CONFIG_MIPS_CMP=y
> 
>   - CONFIG_MIPS_VPE_LOADER_MT cannot be set if CONFIG_MIPS_CMP=y
> 
> But it's simpler to verify correctness if we remove "weak" from the picture
> and test the config symbols directly.
> 
> Remove "weak" from the vpe_run() declaration and use #if to test whether a
> definition should be present.
> 
> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
> ---
>  arch/mips/include/asm/vpe.h |    2 +-
>  arch/mips/kernel/vpe.c      |   10 +++++-----
>  2 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/mips/include/asm/vpe.h b/arch/mips/include/asm/vpe.h
> index 7849f39..80e70db 100644
> --- a/arch/mips/include/asm/vpe.h
> +++ b/arch/mips/include/asm/vpe.h
> @@ -122,7 +122,7 @@ void release_vpe(struct vpe *v);
>  void *alloc_progmem(unsigned long len);
>  void release_progmem(void *ptr);
>  
> -int __weak vpe_run(struct vpe *v);
> +int vpe_run(struct vpe *v);
>  void cleanup_tc(struct tc *tc);
>  
>  int __init vpe_module_init(void);
> diff --git a/arch/mips/kernel/vpe.c b/arch/mips/kernel/vpe.c
> index 72cae9f..04539d6 100644
> --- a/arch/mips/kernel/vpe.c
> +++ b/arch/mips/kernel/vpe.c
> @@ -817,15 +817,11 @@ static int vpe_open(struct inode *inode, struct file *filp)
>  
>  static int vpe_release(struct inode *inode, struct file *filp)
>  {
> +#if defined(CONFIG_MIPS_VPE_LOADER_MT) || defined(CONFIG_MIPS_CMP)

That should be CONFIG_MIPS_VPE_LOADER_CMP, in which case the error case
in the #else bit is always dead code. This file is built only if
CONFIG_MIPS_VPE_LOADER, and the other ones are defined without prompts:

config MIPS_VPE_LOADER_CMP
	bool
	default "y"
	depends on MIPS_VPE_LOADER && MIPS_CMP

config MIPS_VPE_LOADER_MT
	bool
	default "y"
	depends on MIPS_VPE_LOADER && !MIPS_CMP

I.e. one xor the other must be "y" when MIPS_VPE_LOADER=y.

Maybe its worth just removing the weak and the vpe_run check?

Cheers
James

>  	struct vpe *v;
>  	Elf_Ehdr *hdr;
>  	int ret = 0;
>  
> -	if (!vpe_run) {
> -		pr_warn("VPE loader: ELF load failed.\n");
> -		return -ENOEXEC;
> -	}
> -
>  	v = get_vpe(aprp_cpu_index());
>  	if (v == NULL)
>  		return -ENODEV;
> @@ -855,6 +851,10 @@ static int vpe_release(struct inode *inode, struct file *filp)
>  	v->plen = 0;
>  
>  	return ret;
> +#else
> +	pr_warn("VPE loader: ELF load failed.\n");
> +	return -ENOEXEC;
> +#endif
>  }
>  
>  static ssize_t vpe_write(struct file *file, const char __user *buffer,
> 


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