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List:       linux-scsi
Subject:    Re: [PATCH 2/4] lpfc: reduce stack size with CONFIG_GCC_PLUGIN_STRUCTLEAK_VERBOSE
From:       James Smart <james.smart () broadcom ! com>
Date:       2019-06-28 18:57:22
Message-ID: 3027eebb-e49f-6db6-ae0a-39a61c0e34e1 () broadcom ! com
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On 6/28/2019 5:37 AM, Arnd Bergmann wrote:
> The lpfc_debug_dump_all_queues() function repeatedly calls into
> lpfc_debug_dump_qe(), which has a temporary 128 byte buffer.
> This was fine before the introduction of CONFIG_GCC_PLUGIN_STRUCTLEAK_VERBOSE
> because each instance could occupy the same stack slot. However,
> now they each get their own copy, which leads to a huge increase
> in stack usage as seen from the compiler warning:
> 
> drivers/scsi/lpfc/lpfc_debugfs.c: In function 'lpfc_debug_dump_all_queues':
> drivers/scsi/lpfc/lpfc_debugfs.c:6474:1: error: the frame size of 1712 bytes is \
> larger than 100 bytes [-Werror=frame-larger-than=] 
> Avoid this by not marking lpfc_debug_dump_qe() as inline so the
> compiler can choose to emit a static version of this function
> when it's needed or otherwise silently drop it. As an added benefit,
> not inlining multiple copies of this function means we save several
> kilobytes of .text section, reducing the file size from 47kb to 43.
> 
> It is somewhat unusual to have a function that is static but not
> inline in a header file, but this does not cause problems here
> because it is only used by other inline functions. It would
> however seem reasonable to move all the lpfc_debug_dump_* functions
> into lpfc_debugfs.c and not mark them inline as a later cleanup.

I agree with this cleanup.

> 
> Fixes: 81a56f6dcd20 ("gcc-plugins: structleak: Generalize to all variable types")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/scsi/lpfc/lpfc_debugfs.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> 

Reviewed-by: James Smart <james.smart@broadcom.com>

-- james


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