* [PATCH] arm64: Mark functions using explicit register variables as '__always_inline'
@ 2019-10-02 12:37 Will Deacon
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From: Will Deacon @ 2019-10-02 12:37 UTC (permalink / raw)
To: linux-arm-kernel
Cc: Arnd Bergmann, Catalin Marinas, Nick Desaulniers, Russell King,
Masahiro Yamada, Will Deacon, Nicolas Saenz Julienne
As of ac7c3e4ff401 ("compiler: enable CONFIG_OPTIMIZE_INLINING forcibly"),
inline functions are no longer annotated with '__always_inline', which
allows the compiler to decide whether inlining is really a good idea or
not. Although this is a great idea on paper, the reality is that AArch64
GCC prior to 9.1 has been shown to get confused when creating an
out-of-line copy of a function passing explicit 'register' variables
into an inline assembly block:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91111
It's not clear whether this is specific to arm64 or not but, for now,
ensure that all of our functions using 'register' variables are marked
as '__always_inline' so that the old behaviour is effectively preserved.
Hopefully other architectures are luckier with their compilers.
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
I plan to queue this as a fix via the arm64 tree, although I still think
it's papering over a wider issue for us.
arch/arm64/include/asm/atomic_lse.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/atomic_lse.h b/arch/arm64/include/asm/atomic_lse.h
index c6bd87d2915b..574808b9df4c 100644
--- a/arch/arm64/include/asm/atomic_lse.h
+++ b/arch/arm64/include/asm/atomic_lse.h
@@ -321,7 +321,8 @@ static inline s64 __lse_atomic64_dec_if_positive(atomic64_t *v)
}
#define __CMPXCHG_CASE(w, sfx, name, sz, mb, cl...) \
-static inline u##sz __lse__cmpxchg_case_##name##sz(volatile void *ptr, \
+static __always_inline u##sz \
+__lse__cmpxchg_case_##name##sz(volatile void *ptr, \
u##sz old, \
u##sz new) \
{ \
@@ -362,7 +363,8 @@ __CMPXCHG_CASE(x, , mb_, 64, al, "memory")
#undef __CMPXCHG_CASE
#define __CMPXCHG_DBL(name, mb, cl...) \
-static inline long __lse__cmpxchg_double##name(unsigned long old1, \
+static __always_inline long \
+__lse__cmpxchg_double##name(unsigned long old1, \
unsigned long old2, \
unsigned long new1, \
unsigned long new2, \
--
2.23.0.444.g18eeb5a265-goog
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