2022-01-31 11:02:16

by Anders Roxell

Subject: [PATCHv3] powerpc: mm: radix_tlb: rearrange the if-else block

Clang warns:

arch/powerpc/mm/book3s64/radix_tlb.c:1191:23: error: variable 'hstart' is uninitialized when used here [-Werror,-Wuninitialized]
__tlbiel_va_range(hstart, hend, pid,
^~~~~~
arch/powerpc/mm/book3s64/radix_tlb.c:1175:23: note: initialize the variable 'hstart' to silence this warning
unsigned long hstart, hend;
^
= 0
arch/powerpc/mm/book3s64/radix_tlb.c:1191:31: error: variable 'hend' is uninitialized when used here [-Werror,-Wuninitialized]
__tlbiel_va_range(hstart, hend, pid,
^~~~
arch/powerpc/mm/book3s64/radix_tlb.c:1175:29: note: initialize the variable 'hend' to silence this warning
unsigned long hstart, hend;
^
= 0
2 errors generated.

Rework the 'if (IS_ENABLE(CONFIG_TRANSPARENT_HUGEPAGE))' so hstart/hend
always gets initialized, this will silence the warnings. That will also
simplify the 'else' path. Clang is getting confused with these warnings,
but the warnings is a false-positive.

Suggested-by: Arnd Bergmann <[email protected]>
Suggested-by: Nathan Chancellor <[email protected]>
Reviewed-by: Christophe Leroy <[email protected]>
Signed-off-by: Anders Roxell <[email protected]>
---
arch/powerpc/mm/book3s64/radix_tlb.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/mm/book3s64/radix_tlb.c b/arch/powerpc/mm/book3s64/radix_tlb.c
index 7724af19ed7e..5172d5cec2c0 100644
--- a/arch/powerpc/mm/book3s64/radix_tlb.c
+++ b/arch/powerpc/mm/book3s64/radix_tlb.c
@@ -1171,15 +1171,12 @@ static inline void __radix__flush_tlb_range(struct mm_struct *mm,
}
}
} else {
- bool hflush = false;
+ bool hflush;
unsigned long hstart, hend;

- if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
- hstart = (start + PMD_SIZE - 1) & PMD_MASK;
- hend = end & PMD_MASK;
- if (hstart < hend)
- hflush = true;
- }
+ hstart = (start + PMD_SIZE - 1) & PMD_MASK;
+ hend = end & PMD_MASK;
+ hflush = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && hstart < hend;

if (type == FLUSH_TYPE_LOCAL) {
asm volatile("ptesync": : :"memory");
--
2.34.1

2022-01-31 11:11:10

by Nathan Chancellor

Subject: Re: [PATCHv3] powerpc: mm: radix_tlb: rearrange the if-else block

On Fri, Jan 28, 2022 at 02:17:13PM +0100, Anders Roxell wrote:
> Clang warns:
>
> arch/powerpc/mm/book3s64/radix_tlb.c:1191:23: error: variable 'hstart' is uninitialized when used here [-Werror,-Wuninitialized]
> __tlbiel_va_range(hstart, hend, pid,
> ^~~~~~
> arch/powerpc/mm/book3s64/radix_tlb.c:1175:23: note: initialize the variable 'hstart' to silence this warning
> unsigned long hstart, hend;
> ^
> = 0
> arch/powerpc/mm/book3s64/radix_tlb.c:1191:31: error: variable 'hend' is uninitialized when used here [-Werror,-Wuninitialized]
> __tlbiel_va_range(hstart, hend, pid,
> ^~~~
> arch/powerpc/mm/book3s64/radix_tlb.c:1175:29: note: initialize the variable 'hend' to silence this warning
> unsigned long hstart, hend;
> ^
> = 0
> 2 errors generated.
>
> Rework the 'if (IS_ENABLE(CONFIG_TRANSPARENT_HUGEPAGE))' so hstart/hend
> always gets initialized, this will silence the warnings. That will also
> simplify the 'else' path. Clang is getting confused with these warnings,
> but the warnings is a false-positive.
>
> Suggested-by: Arnd Bergmann <[email protected]>
> Suggested-by: Nathan Chancellor <[email protected]>
> Reviewed-by: Christophe Leroy <[email protected]>
> Signed-off-by: Anders Roxell <[email protected]>

Reviewed-by: Nathan Chancellor <[email protected]>

> ---
> arch/powerpc/mm/book3s64/radix_tlb.c | 11 ++++-------
> 1 file changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/arch/powerpc/mm/book3s64/radix_tlb.c b/arch/powerpc/mm/book3s64/radix_tlb.c
> index 7724af19ed7e..5172d5cec2c0 100644
> --- a/arch/powerpc/mm/book3s64/radix_tlb.c
> +++ b/arch/powerpc/mm/book3s64/radix_tlb.c
> @@ -1171,15 +1171,12 @@ static inline void __radix__flush_tlb_range(struct mm_struct *mm,
> }
> }
> } else {
> - bool hflush = false;
> + bool hflush;
> unsigned long hstart, hend;
>
> - if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
> - hstart = (start + PMD_SIZE - 1) & PMD_MASK;
> - hend = end & PMD_MASK;
> - if (hstart < hend)
> - hflush = true;
> - }
> + hstart = (start + PMD_SIZE - 1) & PMD_MASK;
> + hend = end & PMD_MASK;
> + hflush = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && hstart < hend;
>
> if (type == FLUSH_TYPE_LOCAL) {
> asm volatile("ptesync": : :"memory");
> --
> 2.34.1
>