| Message ID | 1395503299-15203-1-git-send-email-behanw@converseincode.com |
|---|---|
| State | New |
| Headers | show |
On Sat, Mar 22, 2014 at 08:48:19AM -0700, behanw@converseincode.com wrote: > From: Behan Webster <behanw@converseincode.com> > > Fix uninitialized return code in default case in cmpxchg-local.h > > This patch fixes the code to prevent an uninitialized return value that is detected > when compiling with clang. The bug produces numerous warnings when compiling the > Linux kernel with clang. > > Signed-off-by: Behan Webster <behanw@converseincode.com> > Signed-off-by: Mark Charlebois <charlebm@gmail.com> > --- > include/asm-generic/cmpxchg-local.h | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/include/asm-generic/cmpxchg-local.h b/include/asm-generic/cmpxchg-local.h > index d8d4c89..9112111 100644 > --- a/include/asm-generic/cmpxchg-local.h > +++ b/include/asm-generic/cmpxchg-local.h > @@ -41,6 +41,7 @@ static inline unsigned long __cmpxchg_local_generic(volatile void *ptr, > break; > default: > wrong_size_cmpxchg(ptr); > + __builtin_unreachable(); It is unreachable() - see compiler.h Sam -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
On Sat, 2014-03-22 at 08:48 -0700, behanw@converseincode.com wrote: > From: Behan Webster <behanw@converseincode.com> > > Fix uninitialized return code in default case in cmpxchg-local.h > > This patch fixes the code to prevent an uninitialized return value that is detected > when compiling with clang. The bug produces numerous warnings when compiling the > Linux kernel with clang. > > Signed-off-by: Behan Webster <behanw@converseincode.com> > Signed-off-by: Mark Charlebois <charlebm@gmail.com> > --- > include/asm-generic/cmpxchg-local.h | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/include/asm-generic/cmpxchg-local.h b/include/asm-generic/cmpxchg-local.h > index d8d4c89..9112111 100644 > --- a/include/asm-generic/cmpxchg-local.h > +++ b/include/asm-generic/cmpxchg-local.h > @@ -41,6 +41,7 @@ static inline unsigned long __cmpxchg_local_generic(volatile void *ptr, > break; > default: > wrong_size_cmpxchg(ptr); > + __builtin_unreachable(); No, that's got to be unreachable() so that it works in all compilers, (__builtin_unreachable is a gcc-4 ism). Got to say this still looks wrong. If wrong_size_cmpxchg() cannot return, the function should be annotated as such with __noreturn (like panic()) so the unreachable() should be superfluous. James -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
On 03/22/14 09:21, Sam Ravnborg wrote: > On Sat, Mar 22, 2014 at 08:48:19AM -0700, behanw@converseincode.com wrote: >> From: Behan Webster <behanw@converseincode.com> >> >> Fix uninitialized return code in default case in cmpxchg-local.h >> >> This patch fixes the code to prevent an uninitialized return value that is detected >> when compiling with clang. The bug produces numerous warnings when compiling the >> Linux kernel with clang. >> >> Signed-off-by: Behan Webster <behanw@converseincode.com> >> Signed-off-by: Mark Charlebois <charlebm@gmail.com> >> --- >> include/asm-generic/cmpxchg-local.h | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/include/asm-generic/cmpxchg-local.h b/include/asm-generic/cmpxchg-local.h >> index d8d4c89..9112111 100644 >> --- a/include/asm-generic/cmpxchg-local.h >> +++ b/include/asm-generic/cmpxchg-local.h >> @@ -41,6 +41,7 @@ static inline unsigned long __cmpxchg_local_generic(volatile void *ptr, >> break; >> default: >> wrong_size_cmpxchg(ptr); >> + __builtin_unreachable(); > It is unreachable() - see compiler.h Oh I see. Behan
On 03/22/14 09:29, James Bottomley wrote: > On Sat, 2014-03-22 at 08:48 -0700, behanw@converseincode.com wrote: >> From: Behan Webster <behanw@converseincode.com> >> >> Fix uninitialized return code in default case in cmpxchg-local.h >> >> This patch fixes the code to prevent an uninitialized return value that is detected >> when compiling with clang. The bug produces numerous warnings when compiling the >> Linux kernel with clang. >> >> Signed-off-by: Behan Webster <behanw@converseincode.com> >> Signed-off-by: Mark Charlebois <charlebm@gmail.com> >> --- >> include/asm-generic/cmpxchg-local.h | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/include/asm-generic/cmpxchg-local.h b/include/asm-generic/cmpxchg-local.h >> index d8d4c89..9112111 100644 >> --- a/include/asm-generic/cmpxchg-local.h >> +++ b/include/asm-generic/cmpxchg-local.h >> @@ -41,6 +41,7 @@ static inline unsigned long __cmpxchg_local_generic(volatile void *ptr, >> break; >> default: >> wrong_size_cmpxchg(ptr); >> + __builtin_unreachable(); > No, that's got to be unreachable() so that it works in all compilers, > (__builtin_unreachable is a gcc-4 ism). It is also supported by clang. > Got to say this still looks wrong. If wrong_size_cmpxchg() cannot > return, the function should be annotated as such with __noreturn (like > panic()) so the unreachable() should be superfluous. Okay. I can try that instead. Thanks, Behan
On 03/22/14 09:42, James Bottomley wrote: > On Sat, 2014-03-22 at 09:37 -0700, Behan Webster wrote: >> On 03/22/14 09:29, James Bottomley wrote: >>> On Sat, 2014-03-22 at 08:48 -0700, behanw@converseincode.com wrote: >>>> From: Behan Webster <behanw@converseincode.com> >>>> >>>> Fix uninitialized return code in default case in cmpxchg-local.h >>>> >>>> This patch fixes the code to prevent an uninitialized return value that is detected >>>> when compiling with clang. The bug produces numerous warnings when compiling the >>>> Linux kernel with clang. >>>> >>>> Signed-off-by: Behan Webster <behanw@converseincode.com> >>>> Signed-off-by: Mark Charlebois <charlebm@gmail.com> >>>> --- >>>> include/asm-generic/cmpxchg-local.h | 1 + >>>> 1 file changed, 1 insertion(+) >>>> >>>> diff --git a/include/asm-generic/cmpxchg-local.h b/include/asm-generic/cmpxchg-local.h >>>> index d8d4c89..9112111 100644 >>>> --- a/include/asm-generic/cmpxchg-local.h >>>> +++ b/include/asm-generic/cmpxchg-local.h >>>> @@ -41,6 +41,7 @@ static inline unsigned long __cmpxchg_local_generic(volatile void *ptr, >>>> break; >>>> default: >>>> wrong_size_cmpxchg(ptr); >>>> + __builtin_unreachable(); >>> No, that's got to be unreachable() so that it works in all compilers, >>> (__builtin_unreachable is a gcc-4 ism). >> It is also supported by clang. > OK, but it's not supported by gcc-3. So gcc-3 would crap out seeing the > statement, which is why we have to wrapper it. Sorry. I wasn't clear. It is not merely a gcc-4 ism; it is also supported by clang. I'm not arguing it should be used. I understand (and agree with) your objection to its use since it isn't supported before gcc-4. >>> Got to say this still looks wrong. If wrong_size_cmpxchg() cannot >>> return, the function should be annotated as such with __noreturn (like >>> panic()) so the unreachable() should be superfluous. >> Okay. I can try that instead. > Great; This seems to work for me (but then my compiler doesn't see the > unreachable problem). > > James > > --- > diff --git a/include/asm-generic/cmpxchg-local.h b/include/asm-generic/cmpxchg-local.h > index d8d4c89..70bef78 100644 > --- a/include/asm-generic/cmpxchg-local.h > +++ b/include/asm-generic/cmpxchg-local.h > @@ -4,7 +4,8 @@ > #include <linux/types.h> > #include <linux/irqflags.h> > > -extern unsigned long wrong_size_cmpxchg(volatile void *ptr); > +extern unsigned long wrong_size_cmpxchg(volatile void *ptr) > + __noreturn; > > /* > * Generic version of __cmpxchg_local (disables interrupts). Takes an unsigned Nice. I'll give it a try. It looks like a much better solution. Behan
diff --git a/include/asm-generic/cmpxchg-local.h b/include/asm-generic/cmpxchg-local.h index d8d4c89..9112111 100644 --- a/include/asm-generic/cmpxchg-local.h +++ b/include/asm-generic/cmpxchg-local.h @@ -41,6 +41,7 @@ static inline unsigned long __cmpxchg_local_generic(volatile void *ptr, break; default: wrong_size_cmpxchg(ptr); + __builtin_unreachable(); } raw_local_irq_restore(flags); return prev;