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]>
Reviewed-by: Nathan Chancellor <[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 4e29b619578c..6d7a1ef723e6 100644
--- a/arch/powerpc/mm/book3s64/radix_tlb.c
+++ b/arch/powerpc/mm/book3s64/radix_tlb.c
@@ -1179,15 +1179,12 @@ 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");
--
2.35.1
Hi!
On Wed, Aug 10, 2022 at 01:43:18PM +0200, 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
This note often is bad advice: hiding problems instead of investigating
and solving them. Bah.
If silencing warnings is your goal, look no further than "-w" :-)
> 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.
If it is, please report that bug to clang? It says "*is* uninitialized
when used here", there can not be false positives to statements like
that. If the analysis was heutistical it should say "may be" or such.
Segher
Anders Roxell <[email protected]> writes:
> 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.
Which version & config are you building?
I don't see this warning in my test builds.
cheers
On Thu, 11 Aug 2022 at 11:41, Michael Ellerman <[email protected]> wrote:
>
> Anders Roxell <[email protected]> writes:
> > 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.
>
> Which version & config are you building?
clang-13, clang-14 and clang-nightly, configs are cell_defconfig and
maple_defconfig
I'm building with tuxmake [1] like this:
$ tuxmake --runtime podman --target-arch powerpc --toolchain clang-14
--kconfig cell_defconfig
Cheers,
Anders
[1] https://tuxmake.org/
On Wed, 10 Aug 2022 13:43:18 +0200, 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.
>
> [...]
Applied to powerpc/next.
[1/1] powerpc: mm: radix_tlb: rearrange the if-else block
https://git.kernel.org/powerpc/c/d78c8e32890ef7eca79ffd67c96022c7f9d8cce4
cheers