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| author | Will Deacon <will.deacon@arm.com> | 2015-03-31 14:11:24 +0100 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2015-07-27 15:28:51 +0100 |
| commit | c8366ba0fb65063b6b4f69c7af1ea74152435590 (patch) | |
| tree | 5e1b7a728baa9428185c8339d33344cf35037b8d /arch/arm64/include/asm/cmpxchg.h | |
| parent | 084f903727e1c3a61d6bcdaeeed30bddc6d7f65a (diff) | |
| download | talos-obmc-linux-c8366ba0fb65063b6b4f69c7af1ea74152435590.tar.gz talos-obmc-linux-c8366ba0fb65063b6b4f69c7af1ea74152435590.zip | |
arm64: xchg: patch in lse instructions when supported by the CPU
On CPUs which support the LSE atomic instructions introduced in ARMv8.1,
it makes sense to use them in preference to ll/sc sequences.
This patch introduces runtime patching of our xchg primitives so that
the LSE swp instruction (yes, you read right!) is used instead.
Reviewed-by: Steve Capper <steve.capper@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/include/asm/cmpxchg.h')
| -rw-r--r-- | arch/arm64/include/asm/cmpxchg.h | 38 |
1 files changed, 33 insertions, 5 deletions
diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h index d8c25b7b18fb..d0cce8068902 100644 --- a/arch/arm64/include/asm/cmpxchg.h +++ b/arch/arm64/include/asm/cmpxchg.h @@ -22,6 +22,7 @@ #include <linux/mmdebug.h> #include <asm/barrier.h> +#include <asm/lse.h> static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size) { @@ -29,37 +30,65 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size switch (size) { case 1: - asm volatile("// __xchg1\n" + asm volatile(ARM64_LSE_ATOMIC_INSN( + /* LL/SC */ "1: ldxrb %w0, %2\n" " stlxrb %w1, %w3, %2\n" " cbnz %w1, 1b\n" + " dmb ish", + /* LSE atomics */ + " nop\n" + " swpalb %w3, %w0, %2\n" + " nop\n" + " nop") : "=&r" (ret), "=&r" (tmp), "+Q" (*(u8 *)ptr) : "r" (x) : "memory"); break; case 2: - asm volatile("// __xchg2\n" + asm volatile(ARM64_LSE_ATOMIC_INSN( + /* LL/SC */ "1: ldxrh %w0, %2\n" " stlxrh %w1, %w3, %2\n" " cbnz %w1, 1b\n" + " dmb ish", + /* LSE atomics */ + " nop\n" + " swpalh %w3, %w0, %2\n" + " nop\n" + " nop") : "=&r" (ret), "=&r" (tmp), "+Q" (*(u16 *)ptr) : "r" (x) : "memory"); break; case 4: - asm volatile("// __xchg4\n" + asm volatile(ARM64_LSE_ATOMIC_INSN( + /* LL/SC */ "1: ldxr %w0, %2\n" " stlxr %w1, %w3, %2\n" " cbnz %w1, 1b\n" + " dmb ish", + /* LSE atomics */ + " nop\n" + " swpal %w3, %w0, %2\n" + " nop\n" + " nop") : "=&r" (ret), "=&r" (tmp), "+Q" (*(u32 *)ptr) : "r" (x) : "memory"); break; case 8: - asm volatile("// __xchg8\n" + asm volatile(ARM64_LSE_ATOMIC_INSN( + /* LL/SC */ "1: ldxr %0, %2\n" " stlxr %w1, %3, %2\n" " cbnz %w1, 1b\n" + " dmb ish", + /* LSE atomics */ + " nop\n" + " swpal %3, %0, %2\n" + " nop\n" + " nop") : "=&r" (ret), "=&r" (tmp), "+Q" (*(u64 *)ptr) : "r" (x) : "memory"); @@ -68,7 +97,6 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size BUILD_BUG(); } - smp_mb(); return ret; } |
