* [PATCH] arm64: percpu: Initialize ret in the default case
@ 2018-09-25 20:24 ` Nick Desaulniers
0 siblings, 0 replies; 10+ messages in thread
From: Nick Desaulniers @ 2018-09-25 20:24 UTC (permalink / raw)
To: linux-arm-kernel
On Tue, Sep 25, 2018 at 12:45 PM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> Clang warns that if the default case is taken, ret will be
> uninitialized.
>
> ./arch/arm64/include/asm/percpu.h:196:2: warning: variable 'ret' is used
> uninitialized whenever switch default is taken
> [-Wsometimes-uninitialized]
> default:
> ^~~~~~~
> ./arch/arm64/include/asm/percpu.h:200:9: note: uninitialized use occurs
> here
> return ret;
> ^~~
> ./arch/arm64/include/asm/percpu.h:157:19: note: initialize the variable
> 'ret' to silence this warning
> unsigned long ret, loop;
> ^
> = 0
>
> This warning appears several times while building the erofs filesystem.
> While it's not strictly wrong, the BUILD_BUG will prevent this from
> becoming a true problem. Initialize ret to 0 in the default case right
> before the BUILD_BUG to silence all of these warnings.
Clang does semantic analysis BEFORE inlining/optimizations, so I can't
determine that default is never reachable. Nathan, thanks for this
patch.
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
>
> Reported-by: Prasad Sodagudi <psodagud@codeaurora.org>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
> arch/arm64/include/asm/percpu.h | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h
> index 9234013e759e..21a81b59a0cc 100644
> --- a/arch/arm64/include/asm/percpu.h
> +++ b/arch/arm64/include/asm/percpu.h
> @@ -96,6 +96,7 @@ static inline unsigned long __percpu_##op(void *ptr, \
> : [val] "Ir" (val)); \
> break; \
> default: \
> + ret = 0; \
> BUILD_BUG(); \
> } \
> \
> @@ -125,6 +126,7 @@ static inline unsigned long __percpu_read(void *ptr, int size)
> ret = READ_ONCE(*(u64 *)ptr);
> break;
> default:
> + ret = 0;
> BUILD_BUG();
> }
>
> @@ -194,6 +196,7 @@ static inline unsigned long __percpu_xchg(void *ptr, unsigned long val,
> : [val] "r" (val));
> break;
> default:
> + ret = 0;
> BUILD_BUG();
> }
>
> --
> 2.19.0
>
--
Thanks,
~Nick Desaulniers
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] arm64: percpu: Initialize ret in the default case
2018-09-25 20:24 ` Nick Desaulniers
@ 2018-09-25 20:29 ` Nick Desaulniers
-1 siblings, 0 replies; 10+ messages in thread
From: Nick Desaulniers @ 2018-09-25 20:29 UTC (permalink / raw)
To: Nathan Chancellor
Cc: dennis, tj, Christoph Lameter, Catalin Marinas, Will Deacon,
Linux ARM, LKML, psodagud
On Tue, Sep 25, 2018 at 1:24 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Tue, Sep 25, 2018 at 12:45 PM Nathan Chancellor
> <natechancellor@gmail.com> wrote:
> >
> > Clang warns that if the default case is taken, ret will be
> > uninitialized.
> >
> > ./arch/arm64/include/asm/percpu.h:196:2: warning: variable 'ret' is used
> > uninitialized whenever switch default is taken
> > [-Wsometimes-uninitialized]
> > default:
> > ^~~~~~~
> > ./arch/arm64/include/asm/percpu.h:200:9: note: uninitialized use occurs
> > here
> > return ret;
> > ^~~
> > ./arch/arm64/include/asm/percpu.h:157:19: note: initialize the variable
> > 'ret' to silence this warning
> > unsigned long ret, loop;
> > ^
> > = 0
> >
> > This warning appears several times while building the erofs filesystem.
> > While it's not strictly wrong, the BUILD_BUG will prevent this from
> > becoming a true problem. Initialize ret to 0 in the default case right
> > before the BUILD_BUG to silence all of these warnings.
>
> Clang does semantic analysis BEFORE inlining/optimizations, so I can't
s/I/it/
> determine that default is never reachable. Nathan, thanks for this
> patch.
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
>
> >
> > Reported-by: Prasad Sodagudi <psodagud@codeaurora.org>
> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> > ---
> > arch/arm64/include/asm/percpu.h | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h
> > index 9234013e759e..21a81b59a0cc 100644
> > --- a/arch/arm64/include/asm/percpu.h
> > +++ b/arch/arm64/include/asm/percpu.h
> > @@ -96,6 +96,7 @@ static inline unsigned long __percpu_##op(void *ptr, \
> > : [val] "Ir" (val)); \
> > break; \
> > default: \
> > + ret = 0; \
> > BUILD_BUG(); \
> > } \
> > \
> > @@ -125,6 +126,7 @@ static inline unsigned long __percpu_read(void *ptr, int size)
> > ret = READ_ONCE(*(u64 *)ptr);
> > break;
> > default:
> > + ret = 0;
> > BUILD_BUG();
> > }
> >
> > @@ -194,6 +196,7 @@ static inline unsigned long __percpu_xchg(void *ptr, unsigned long val,
> > : [val] "r" (val));
> > break;
> > default:
> > + ret = 0;
> > BUILD_BUG();
> > }
> >
> > --
> > 2.19.0
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers
--
Thanks,
~Nick Desaulniers
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH] arm64: percpu: Initialize ret in the default case
@ 2018-09-25 20:29 ` Nick Desaulniers
0 siblings, 0 replies; 10+ messages in thread
From: Nick Desaulniers @ 2018-09-25 20:29 UTC (permalink / raw)
To: linux-arm-kernel
On Tue, Sep 25, 2018 at 1:24 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Tue, Sep 25, 2018 at 12:45 PM Nathan Chancellor
> <natechancellor@gmail.com> wrote:
> >
> > Clang warns that if the default case is taken, ret will be
> > uninitialized.
> >
> > ./arch/arm64/include/asm/percpu.h:196:2: warning: variable 'ret' is used
> > uninitialized whenever switch default is taken
> > [-Wsometimes-uninitialized]
> > default:
> > ^~~~~~~
> > ./arch/arm64/include/asm/percpu.h:200:9: note: uninitialized use occurs
> > here
> > return ret;
> > ^~~
> > ./arch/arm64/include/asm/percpu.h:157:19: note: initialize the variable
> > 'ret' to silence this warning
> > unsigned long ret, loop;
> > ^
> > = 0
> >
> > This warning appears several times while building the erofs filesystem.
> > While it's not strictly wrong, the BUILD_BUG will prevent this from
> > becoming a true problem. Initialize ret to 0 in the default case right
> > before the BUILD_BUG to silence all of these warnings.
>
> Clang does semantic analysis BEFORE inlining/optimizations, so I can't
s/I/it/
> determine that default is never reachable. Nathan, thanks for this
> patch.
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
>
> >
> > Reported-by: Prasad Sodagudi <psodagud@codeaurora.org>
> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> > ---
> > arch/arm64/include/asm/percpu.h | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h
> > index 9234013e759e..21a81b59a0cc 100644
> > --- a/arch/arm64/include/asm/percpu.h
> > +++ b/arch/arm64/include/asm/percpu.h
> > @@ -96,6 +96,7 @@ static inline unsigned long __percpu_##op(void *ptr, \
> > : [val] "Ir" (val)); \
> > break; \
> > default: \
> > + ret = 0; \
> > BUILD_BUG(); \
> > } \
> > \
> > @@ -125,6 +126,7 @@ static inline unsigned long __percpu_read(void *ptr, int size)
> > ret = READ_ONCE(*(u64 *)ptr);
> > break;
> > default:
> > + ret = 0;
> > BUILD_BUG();
> > }
> >
> > @@ -194,6 +196,7 @@ static inline unsigned long __percpu_xchg(void *ptr, unsigned long val,
> > : [val] "r" (val));
> > break;
> > default:
> > + ret = 0;
> > BUILD_BUG();
> > }
> >
> > --
> > 2.19.0
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers
--
Thanks,
~Nick Desaulniers
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] arm64: percpu: Initialize ret in the default case
2018-09-25 20:24 ` Nick Desaulniers
@ 2018-09-25 20:35 ` Dennis Zhou
-1 siblings, 0 replies; 10+ messages in thread
From: Dennis Zhou @ 2018-09-25 20:35 UTC (permalink / raw)
To: Nick Desaulniers
Cc: Nathan Chancellor, tj, Christoph Lameter, Catalin Marinas,
Will Deacon, Linux ARM, LKML, psodagud
Hi Nick,
On Tue, Sep 25, 2018 at 01:24:06PM -0700, Nick Desaulniers wrote:
> On Tue, Sep 25, 2018 at 12:45 PM Nathan Chancellor
> <natechancellor@gmail.com> wrote:
> >
> > Clang warns that if the default case is taken, ret will be
> > uninitialized.
> >
> > ./arch/arm64/include/asm/percpu.h:196:2: warning: variable 'ret' is used
> > uninitialized whenever switch default is taken
> > [-Wsometimes-uninitialized]
> > default:
> > ^~~~~~~
> > ./arch/arm64/include/asm/percpu.h:200:9: note: uninitialized use occurs
> > here
> > return ret;
> > ^~~
> > ./arch/arm64/include/asm/percpu.h:157:19: note: initialize the variable
> > 'ret' to silence this warning
> > unsigned long ret, loop;
> > ^
> > = 0
> >
> > This warning appears several times while building the erofs filesystem.
> > While it's not strictly wrong, the BUILD_BUG will prevent this from
> > becoming a true problem. Initialize ret to 0 in the default case right
> > before the BUILD_BUG to silence all of these warnings.
>
> Clang does semantic analysis BEFORE inlining/optimizations, so I can't
> determine that default is never reachable. Nathan, thanks for this
> patch.
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
>
Thanks for the explanation!
Dennis
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH] arm64: percpu: Initialize ret in the default case
@ 2018-09-25 20:35 ` Dennis Zhou
0 siblings, 0 replies; 10+ messages in thread
From: Dennis Zhou @ 2018-09-25 20:35 UTC (permalink / raw)
To: linux-arm-kernel
Hi Nick,
On Tue, Sep 25, 2018 at 01:24:06PM -0700, Nick Desaulniers wrote:
> On Tue, Sep 25, 2018 at 12:45 PM Nathan Chancellor
> <natechancellor@gmail.com> wrote:
> >
> > Clang warns that if the default case is taken, ret will be
> > uninitialized.
> >
> > ./arch/arm64/include/asm/percpu.h:196:2: warning: variable 'ret' is used
> > uninitialized whenever switch default is taken
> > [-Wsometimes-uninitialized]
> > default:
> > ^~~~~~~
> > ./arch/arm64/include/asm/percpu.h:200:9: note: uninitialized use occurs
> > here
> > return ret;
> > ^~~
> > ./arch/arm64/include/asm/percpu.h:157:19: note: initialize the variable
> > 'ret' to silence this warning
> > unsigned long ret, loop;
> > ^
> > = 0
> >
> > This warning appears several times while building the erofs filesystem.
> > While it's not strictly wrong, the BUILD_BUG will prevent this from
> > becoming a true problem. Initialize ret to 0 in the default case right
> > before the BUILD_BUG to silence all of these warnings.
>
> Clang does semantic analysis BEFORE inlining/optimizations, so I can't
> determine that default is never reachable. Nathan, thanks for this
> patch.
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
>
Thanks for the explanation!
Dennis
^ permalink raw reply [flat|nested] 10+ messages in thread