Re: [PATCH] powerpc/machdep: warn when machine_is() used too early
Michael Ellerman writes:
> Christophe Leroy writes:
>> Le 11/02/2023 à 00:56, Nathan Lynch via B4 Submission Endpoint a écrit :
>>> From: Nathan Lynch
>>>
>>> machine_is() can't provide correct results before probe_machine() has
>>> run. Warn when it's used too early in boot.
>>>
>>> Signed-off-by: Nathan Lynch
>>> ---
>>> Prompted by my attempts to do some pseries-specific setup during
>>> rtas_initialize() and being puzzled for a while that it wasn't
>>> working.
>>> ---
>>> arch/powerpc/include/asm/machdep.h | 12 +++-
>>> 1 file changed, 7 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/arch/powerpc/include/asm/machdep.h
>>> b/arch/powerpc/include/asm/machdep.h
>>> index 378b8d5836a7..8c0a799d18cd 100644
>>> --- a/arch/powerpc/include/asm/machdep.h
>>> +++ b/arch/powerpc/include/asm/machdep.h
>>> @@ -220,11 +220,13 @@ 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 == _##name; \
>>> +#define machine_is(name)\
>>> + ({ \
>>> + extern struct machdep_calls mach_##name \
>>> + __attribute__((weak)); \
>>> + WARN(!machine_id, \
>>> +"machine_is() called before probe_machine()"); \
>>
>> Is a WARN() really necessary ? WARN() is less optimised than WARN_ON(),
>> especially on PPC64.
>>
>> This should never ever happen so a WARN_ON(!machine_id) should be
>> enough, the developper that hits it is able to go to the given file:line
>> and understand what happened.
>
> Yeah I agree, WARN_ON() should be sufficient here, and should generate
> slightly better code. We have > 100 uses of machine_is(), so keeping
> each small is desirable.
Sure, I'll change it.
Re: [PATCH] powerpc/machdep: warn when machine_is() used too early
Christophe Leroy writes:
> Le 11/02/2023 à 00:56, Nathan Lynch via B4 Submission Endpoint a écrit :
>> From: Nathan Lynch
>>
>> machine_is() can't provide correct results before probe_machine() has
>> run. Warn when it's used too early in boot.
>>
>> Signed-off-by: Nathan Lynch
>> ---
>> Prompted by my attempts to do some pseries-specific setup during
>> rtas_initialize() and being puzzled for a while that it wasn't
>> working.
>> ---
>> arch/powerpc/include/asm/machdep.h | 12 +++-
>> 1 file changed, 7 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/machdep.h
>> b/arch/powerpc/include/asm/machdep.h
>> index 378b8d5836a7..8c0a799d18cd 100644
>> --- a/arch/powerpc/include/asm/machdep.h
>> +++ b/arch/powerpc/include/asm/machdep.h
>> @@ -220,11 +220,13 @@ 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 == _##name; \
>> +#define machine_is(name)\
>> +({ \
>> +extern struct machdep_calls mach_##name \
>> +__attribute__((weak)); \
>> +WARN(!machine_id, \
>> + "machine_is() called before probe_machine()"); \
>
> Is a WARN() really necessary ? WARN() is less optimised than WARN_ON(),
> especially on PPC64.
>
> This should never ever happen so a WARN_ON(!machine_id) should be
> enough, the developper that hits it is able to go to the given file:line
> and understand what happened.
Yeah I agree, WARN_ON() should be sufficient here, and should generate
slightly better code. We have > 100 uses of machine_is(), so keeping
each small is desirable.
cheers
Re: [PATCH] powerpc/machdep: warn when machine_is() used too early
Le 11/02/2023 à 00:56, Nathan Lynch via B4 Submission Endpoint a écrit :
> From: Nathan Lynch
>
> machine_is() can't provide correct results before probe_machine() has
> run. Warn when it's used too early in boot.
>
> Signed-off-by: Nathan Lynch
> ---
> Prompted by my attempts to do some pseries-specific setup during
> rtas_initialize() and being puzzled for a while that it wasn't
> working.
> ---
> arch/powerpc/include/asm/machdep.h | 12 +++-
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/machdep.h
> b/arch/powerpc/include/asm/machdep.h
> index 378b8d5836a7..8c0a799d18cd 100644
> --- a/arch/powerpc/include/asm/machdep.h
> +++ b/arch/powerpc/include/asm/machdep.h
> @@ -220,11 +220,13 @@ 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 == _##name; \
> +#define machine_is(name)\
> + ({ \
> + extern struct machdep_calls mach_##name \
> + __attribute__((weak)); \
> + WARN(!machine_id, \
> + "machine_is() called before probe_machine()"); \
Is a WARN() really necessary ? WARN() is less optimised than WARN_ON(),
especially on PPC64.
This should never ever happen so a WARN_ON(!machine_id) should be
enough, the developper that hits it is able to go to the given file:line
and understand what happened.
> + machine_id == _##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,
