[PATCH v2] powerpc/machdep: warn when machine_is() used too early

[Christophe Leroy]

Le 13/02/2023 à 20:23, Nathan Lynch via B4 Submission Endpoint a écrit :
> From: Nathan Lynch <nathanl at linux.ibm.com>
> 
> machine_is() can't provide correct results before probe_machine() has
> run. Warn when it's used too early in boot, placing the WARN_ON() in a
> helper function so the reported file:line indicates exactly what went
> wrong.
> 
> checkpatch complains about __attribute__((weak)) in the patch, so
> change that to __weak, and align the line continuations as well.
> 
> Signed-off-by: Nathan Lynch <nathanl at linux.ibm.com>

Reviewed-by: Christophe Leroy <christophe.leroy at csgroup.eu>

> ---
> Prompted by my attempts to do some pseries-specific setup during
> rtas_initialize() and being puzzled for a while that it wasn't
> working.
> 
> Changes in v2:
> - Use WARN_ON(), not WARN().
> - Introduce __machine_is() helper function so the line reported is
>    accurate.
> - Update __attribute__((weak)) to __weak for checkpatch's sake.
> - Link to v1: https://lore.kernel.org/r/20230210-warn-on-machine-is-before-probe-machine-v1-1-f0cba57125fb@linux.ibm.com
> ---
>   arch/powerpc/include/asm/machdep.h | 16 +++++++++++-----
>   1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/machdep.h b/arch/powerpc/include/asm/machdep.h
> index 378b8d5836a7..459736d5e511 100644
> --- a/arch/powerpc/include/asm/machdep.h
> +++ b/arch/powerpc/include/asm/machdep.h
> @@ -3,6 +3,7 @@
>   #define _ASM_POWERPC_MACHDEP_H
>   #ifdef __KERNEL__
>   
> +#include <linux/compiler.h>
>   #include <linux/seq_file.h>
>   #include <linux/init.h>
>   #include <linux/dma-mapping.h>
> @@ -220,11 +221,16 @@ extern struct machdep_calls *machine_id;
>   	EXPORT_SYMBOL(mach_##name);				\
>   	struct machdep_calls mach_##name __machine_desc =
>   
> -#define machine_is(name) \
> -	({ \
> -		extern struct machdep_calls mach_##name \
> -			__attribute__((weak));		 \
> -		machine_id == &mach_##name; \
> +static inline bool __machine_is(const struct machdep_calls *md)
> +{
> +	WARN_ON(!machine_id); // complain if used before probe_machine()
> +	return machine_id == md;
> +}
> +
> +#define machine_is(name)                                        \

Misaligned back-slash ?

> +	({                                                      \
> +		extern struct machdep_calls mach_##name __weak; \
> +		__machine_is(&mach_##name);                     \
>   	})
>   
>   static inline void log_error(char *buf, unsigned int err_type, int fatal)
> 
> ---
> base-commit: 0bfb97203f5f300777624a2ad6f8f84aea3e8658
> change-id: 20230210-warn-on-machine-is-before-probe-machine-37515b1f43bb
> 
> Best regards,