Re: [PATCHv3, resend] powerpc: mm: radix_tlb: rearrange the if-else block
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
Re: [PATCHv3, resend] powerpc: mm: radix_tlb: rearrange the if-else block
On Thu, 11 Aug 2022 at 11:41, Michael Ellerman wrote: > > Anders Roxell 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/
Re: [PATCHv3, resend] powerpc: mm: radix_tlb: rearrange the if-else block
Anders Roxell 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
Re: [PATCHv3, resend] powerpc: mm: radix_tlb: rearrange the if-else block
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
[PATCHv3, resend] 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
Suggested-by: Nathan Chancellor
Reviewed-by: Christophe Leroy
Reviewed-by: Nathan Chancellor
Signed-off-by: Anders Roxell
---
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
