Re: [PATCH 2/4] lpfc: reduce stack size with CONFIG_GCC_PLUGIN_STRUCTLEAK_VERBOSE

[James Smart]

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@xxxxxxxx>
> ---
>   drivers/scsi/lpfc/lpfc_debugfs.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)

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

-- james