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author | Will Deacon <will.deacon@arm.com> | 2015-05-29 14:26:59 +0100 |
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committer | Will Deacon <will.deacon@arm.com> | 2015-07-27 15:28:52 +0100 |
commit | 0bc671d3f4bee9c31110d096ada0de52380e693d (patch) | |
tree | 63c5120264072fa4599fc6fe0f92f6a044d48f0c /arch/arm64/include/asm/atomic_ll_sc.h | |
parent | e9a4b795652f654a7870727e5333c1b709b8736c (diff) | |
download | linux-0bc671d3f4bee9c31110d096ada0de52380e693d.tar.bz2 |
arm64: cmpxchg: avoid "cc" clobber in ll/sc routines
We can perform the cmpxchg comparison using eor and cbnz which avoids
the "cc" clobber for the ll/sc case and consequently for the LSE case
where we may have to fall-back on the ll/sc code at runtime.
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/atomic_ll_sc.h')
-rw-r--r-- | arch/arm64/include/asm/atomic_ll_sc.h | 14 |
1 files changed, 6 insertions, 8 deletions
diff --git a/arch/arm64/include/asm/atomic_ll_sc.h b/arch/arm64/include/asm/atomic_ll_sc.h index f89f1e4ba577..c02684d1eab3 100644 --- a/arch/arm64/include/asm/atomic_ll_sc.h +++ b/arch/arm64/include/asm/atomic_ll_sc.h @@ -101,14 +101,13 @@ __LL_SC_PREFIX(atomic_cmpxchg(atomic_t *ptr, int old, int new)) asm volatile("// atomic_cmpxchg\n" "1: ldxr %w1, %2\n" -" cmp %w1, %w3\n" -" b.ne 2f\n" +" eor %w0, %w1, %w3\n" +" cbnz %w0, 2f\n" " stxr %w0, %w4, %2\n" " cbnz %w0, 1b\n" "2:" : "=&r" (tmp), "=&r" (oldval), "+Q" (ptr->counter) - : "Ir" (old), "r" (new) - : "cc"); + : "Lr" (old), "r" (new)); smp_mb(); return oldval; @@ -179,14 +178,13 @@ __LL_SC_PREFIX(atomic64_cmpxchg(atomic64_t *ptr, long old, long new)) asm volatile("// atomic64_cmpxchg\n" "1: ldxr %1, %2\n" -" cmp %1, %3\n" -" b.ne 2f\n" +" eor %0, %1, %3\n" +" cbnz %w0, 2f\n" " stxr %w0, %4, %2\n" " cbnz %w0, 1b\n" "2:" : "=&r" (res), "=&r" (oldval), "+Q" (ptr->counter) - : "Ir" (old), "r" (new) - : "cc"); + : "Lr" (old), "r" (new)); smp_mb(); return oldval; |