linux-kernel - [PATCH v2 12/27] locking/atomic: x86: add preprocessor symbols

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Message-Id: <20230605070124.3741859-13-mark.rutland@arm.com>
Date:   Mon,  5 Jun 2023 08:01:09 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     linux-kernel@...r.kernel.org
Cc:     akiyks@...il.com, boqun.feng@...il.com, corbet@....net,
        keescook@...omium.org, linux@...linux.org.uk,
        linux-doc@...r.kernel.org, mark.rutland@....com,
        mchehab@...nel.org, paulmck@...nel.org, peterz@...radead.org,
        rdunlap@...radead.org, sstabellini@...nel.org, will@...nel.org
Subject: [PATCH v2 12/27] locking/atomic: x86: add preprocessor symbols

Some atomics can be implemented in several different ways, e.g.
FULL/ACQUIRE/RELEASE ordered atomics can be implemented in terms of
RELAXED atomics, and ACQUIRE/RELEASE/RELAXED can be implemented in terms
of FULL ordered atomics. Other atomics are optional, and don't exist in
some configurations (e.g. not all architectures implement the 128-bit
cmpxchg ops).

Subsequent patches will require that architectures define a preprocessor
symbol for any atomic (or ordering variant) which is optional. This will
make the fallback ifdeffery more robust, and simplify future changes.

Add the required definitions to arch/x86.

Signed-off-by: Mark Rutland <mark.rutland@....com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Cc: Boqun Feng <boqun.feng@...il.com>
Cc: Paul E. McKenney <paulmck@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Will Deacon <will@...nel.org>
---
 arch/x86/include/asm/cmpxchg_64.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/include/asm/cmpxchg_64.h b/arch/x86/include/asm/cmpxchg_64.h
index 3e6e3eef701b3..44b08b53ab32f 100644
--- a/arch/x86/include/asm/cmpxchg_64.h
+++ b/arch/x86/include/asm/cmpxchg_64.h
@@ -45,11 +45,13 @@ static __always_inline u128 arch_cmpxchg128(volatile u128 *ptr, u128 old, u128 n
 {
 	return __arch_cmpxchg128(ptr, old, new, LOCK_PREFIX);
 }
+#define arch_cmpxchg128 arch_cmpxchg128
 
 static __always_inline u128 arch_cmpxchg128_local(volatile u128 *ptr, u128 old, u128 new)
 {
 	return __arch_cmpxchg128(ptr, old, new,);
 }
+#define arch_cmpxchg128_local arch_cmpxchg128_local
 
 #define __arch_try_cmpxchg128(_ptr, _oldp, _new, _lock)			\
 ({									\
@@ -75,11 +77,13 @@ static __always_inline bool arch_try_cmpxchg128(volatile u128 *ptr, u128 *oldp,
 {
 	return __arch_try_cmpxchg128(ptr, oldp, new, LOCK_PREFIX);
 }
+#define arch_try_cmpxchg128 arch_try_cmpxchg128
 
 static __always_inline bool arch_try_cmpxchg128_local(volatile u128 *ptr, u128 *oldp, u128 new)
 {
 	return __arch_try_cmpxchg128(ptr, oldp, new,);
 }
+#define arch_try_cmpxchg128_local arch_try_cmpxchg128_local
 
 #define system_has_cmpxchg128()		boot_cpu_has(X86_FEATURE_CX16)
 
-- 
2.30.2