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

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Date:	Mon, 13 Jul 2015 16:35:15 -0500
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	James Hogan <james.hogan@...tec.com>
Cc:	Ralf Baechle <ralf@...ux-mips.org>,
	Andrew Bresticker <abrestic@...omium.org>,
	"linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/9] MIPS: MT: Remove "weak" from vpe_run() declaration

On Mon, Jul 13, 2015 at 5:27 AM, James Hogan <james.hogan@...tec.com> wrote:
> 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?

Yes, thanks a lot for clearing up my Kconfig confusion!

>>       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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