[PATCH] ACPI: Eliminate usage of uninitialized_var() macro

[PATCH] ACPI: Eliminate usage of uninitialized_var() macro

[Jason Yan]

This is an effort to eliminate the uninitialized_var() macro[1].

The use of this macro is the wrong solution because it forces off ANY
analysis by the compiler for a given variable. It even masks "unused
variable" warnings.

Quoted from Linus[2]:

"It's a horrible thing to use, in that it adds extra cruft to the
source code, and then shuts up a compiler warning (even the _reliable_
warnings from gcc)."

The gcc option "-Wmaybe-uninitialized" has been disabled and this change
will not produce any warnnings even with "make W=1".

[1] https://github.com/KSPP/linux/issues/81
[2] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
---
 drivers/acpi/acpi_pad.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c
index e7dc0133f817..6cc4c92d9ff9 100644
--- a/drivers/acpi/acpi_pad.c
+++ b/drivers/acpi/acpi_pad.c
@@ -88,7 +88,7 @@ static void round_robin_cpu(unsigned int tsk_index)
 	cpumask_var_t tmp;
 	int cpu;
 	unsigned long min_weight = -1;
-	unsigned long uninitialized_var(preferred_cpu);
+	unsigned long preferred_cpu;
 
 	if (!alloc_cpumask_var(&tmp, GFP_KERNEL))
 		return;
-- 
2.25.4

Re: [PATCH] ACPI: Eliminate usage of uninitialized_var() macro

[Rafael J. Wysocki]

On Monday, June 15, 2020 6:00:47 AM CEST Jason Yan wrote:
> This is an effort to eliminate the uninitialized_var() macro[1].
> 
> The use of this macro is the wrong solution because it forces off ANY
> analysis by the compiler for a given variable. It even masks "unused
> variable" warnings.
> 
> Quoted from Linus[2]:
> 
> "It's a horrible thing to use, in that it adds extra cruft to the
> source code, and then shuts up a compiler warning (even the _reliable_
> warnings from gcc)."
> 
> The gcc option "-Wmaybe-uninitialized" has been disabled and this change
> will not produce any warnnings even with "make W=1".
> 
> [1] https://github.com/KSPP/linux/issues/81
> [2] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/
> 
> Cc: Kees Cook <keescook@chromium.org>
> Signed-off-by: Jason Yan <yanaijie@huawei.com>
> ---
>  drivers/acpi/acpi_pad.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c
> index e7dc0133f817..6cc4c92d9ff9 100644
> --- a/drivers/acpi/acpi_pad.c
> +++ b/drivers/acpi/acpi_pad.c
> @@ -88,7 +88,7 @@ static void round_robin_cpu(unsigned int tsk_index)
>  	cpumask_var_t tmp;
>  	int cpu;
>  	unsigned long min_weight = -1;
> -	unsigned long uninitialized_var(preferred_cpu);
> +	unsigned long preferred_cpu;
>  
>  	if (!alloc_cpumask_var(&tmp, GFP_KERNEL))
>  		return;
> 

Applied as 5.9 material, thanks!