On Mon, Sep 09, 2019 at 10:21:35PM +0200, Arnd Bergmann wrote: > On arm64 build with clang, sometimes the __cmpxchg_mb is not inlined > when CONFIG_OPTIMIZE_INLINING is set. > Clang then fails a compile-time assertion, because it cannot tell at > compile time what the size of the argument is: > > mm/memcontrol.o: In function `__cmpxchg_mb': > memcontrol.c:(.text+0x1a4c): undefined reference to `__compiletime_assert_175' > memcontrol.c:(.text+0x1a4c): relocation truncated to fit: R_AARCH64_CALL26 > against undefined symbol `__compiletime_assert_175' > > Mark all of the cmpxchg() style functions as __always_inline to > ensure that the compiler can see the result. > > Signed-off-by: Arnd Bergmann <a...@arndb.de> > ---
I was able to reproduce this with the following: $ git describe HEAD next-20190904 $ clang --version Android (5821526 based on r365631) clang version 9.0.6 (https://android.googlesource.com/toolchain/llvm-project 85305eaf1e90ff529d304abac8a979e1d967f0a2) (based on LLVM 9.0.6svn) Target: x86_64-unknown-linux-gnu Thread model: posix InstalledDir: /home/andrewm/android-clang/clang-r365631/bin $ make O=~/linux-build/ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- CC=clang -j56 allyesconfig Image (I was unable to reproduce with defconfig+OPTIMIZE_INLINING). However... > arch/arm64/include/asm/cmpxchg.h | 15 ++++++++------- > 1 file changed, 8 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/include/asm/cmpxchg.h > b/arch/arm64/include/asm/cmpxchg.h > index a1398f2f9994..fd64dc8a235f 100644 > --- a/arch/arm64/include/asm/cmpxchg.h > +++ b/arch/arm64/include/asm/cmpxchg.h > @@ -19,7 +19,7 @@ > * acquire+release for the latter. > */ > #define __XCHG_CASE(w, sfx, name, sz, mb, nop_lse, acq, acq_lse, rel, cl) > \ > -static inline u##sz __xchg_case_##name##sz(u##sz x, volatile void *ptr) > \ > +static __always_inline u##sz __xchg_case_##name##sz(u##sz x, volatile void > *ptr)\ This hunk isn't needed, there is no BUILD_BUG here. > { > \ > u##sz ret; > \ > unsigned long tmp; > \ > @@ -62,7 +62,7 @@ __XCHG_CASE( , , mb_, 64, dmb ish, nop, , a, l, "memory") > #undef __XCHG_CASE > > #define __XCHG_GEN(sfx) > \ > -static inline unsigned long __xchg##sfx(unsigned long x, \ > +static __always_inline unsigned long __xchg##sfx(unsigned long x, \ > volatile void *ptr, \ > int size) \ > { \ > @@ -103,8 +103,9 @@ __XCHG_GEN(_mb) > #define arch_xchg_release(...) __xchg_wrapper(_rel, __VA_ARGS__) > #define arch_xchg(...) __xchg_wrapper( _mb, __VA_ARGS__) > > -#define __CMPXCHG_CASE(name, sz) \ > -static inline u##sz __cmpxchg_case_##name##sz(volatile void *ptr, \ > +#define __CMPXCHG_CASE(name, sz) \ > +static __always_inline u##sz > \ > +__cmpxchg_case_##name##sz(volatile void *ptr, > \ This hunk isn't needed, there is no BUILD_BUG here. > u##sz old, \ > u##sz new) \ > { \ > @@ -148,7 +149,7 @@ __CMPXCHG_DBL(_mb) > #undef __CMPXCHG_DBL > > #define __CMPXCHG_GEN(sfx) \ > -static inline unsigned long __cmpxchg##sfx(volatile void *ptr, > \ > +static __always_inline unsigned long __cmpxchg##sfx(volatile void *ptr, > \ > unsigned long old, \ > unsigned long new, \ > int size) \ > @@ -230,7 +231,7 @@ __CMPXCHG_GEN(_mb) > }) > > #define __CMPWAIT_CASE(w, sfx, sz) \ > -static inline void __cmpwait_case_##sz(volatile void *ptr, \ > +static __always_inline void __cmpwait_case_##sz(volatile void *ptr, \ > unsigned long val) \ This hunk isn't needed, there is no BUILD_BUG here. > { \ > unsigned long tmp; \ > @@ -255,7 +256,7 @@ __CMPWAIT_CASE( , , 64); > #undef __CMPWAIT_CASE > > #define __CMPWAIT_GEN(sfx) \ > -static inline void __cmpwait##sfx(volatile void *ptr, > \ > +static __always_inline void __cmpwait##sfx(volatile void *ptr, > \ > unsigned long val, \ > int size) \ > { \ Alternatively is it possible to replace the BUILD_BUG's with something else? I think because we use BUILD_BUG at the end of a switch statement, we make the assumption that size is known at compile time, for this reason we should ensure the function containing the BUILD_BUG is __always_inline. Looking across the kernel where BUILD_BUG is used as a default in a switch statment ($ git grep -B 3 BUILD_BUG\( | grep default), most instances are within macros, but many are found in an __always_inline function: arch/x86/kvm/cpuid.h mm/kasan/generic.c Though some are not: include/linux/signal.h arch/arm64/include/asm/arm_dsu/pmu.h I wonder if there may be a latent mole ready to whack with pmu.h? Anyway with just the three remaining hunks: Reviewed-by: Andrew Murray <andrew.mur...@arm.com> Tested-by: Andrew Murray <andrew.mur...@arm.com> > -- > 2.20.0 >
