arm64: Atomic operations
This patch introduces the atomic, mutex and futex operations. Many
atomic operations use the load-acquire and store-release operations
which imply barriers, avoiding the need for explicit DMB.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
diff --git a/arch/arm64/include/asm/atomic.h b/arch/arm64/include/asm/atomic.h
new file mode 100644
index 0000000..407717b
--- /dev/null
+++ b/arch/arm64/include/asm/atomic.h
@@ -0,0 +1,305 @@
+/*
+ * Based on arch/arm/include/asm/atomic.h
+ *
+ * Copyright (C) 1996 Russell King.
+ * Copyright (C) 2002 Deep Blue Solutions Ltd.
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_ATOMIC_H
+#define __ASM_ATOMIC_H
+
+#include <linux/compiler.h>
+#include <linux/types.h>
+
+#include <asm/barrier.h>
+#include <asm/cmpxchg.h>
+
+#define ATOMIC_INIT(i) { (i) }
+
+#ifdef __KERNEL__
+
+/*
+ * On ARM, ordinary assignment (str instruction) doesn't clear the local
+ * strex/ldrex monitor on some implementations. The reason we can use it for
+ * atomic_set() is the clrex or dummy strex done on every exception return.
+ */
+#define atomic_read(v) (*(volatile int *)&(v)->counter)
+#define atomic_set(v,i) (((v)->counter) = (i))
+
+/*
+ * AArch64 UP and SMP safe atomic ops. We use load exclusive and
+ * store exclusive to ensure that these are atomic. We may loop
+ * to ensure that the update happens.
+ */
+static inline void atomic_add(int i, atomic_t *v)
+{
+ unsigned long tmp;
+ int result;
+
+ asm volatile("// atomic_add\n"
+"1: ldxr %w0, [%3]\n"
+" add %w0, %w0, %w4\n"
+" stxr %w1, %w0, [%3]\n"
+" cbnz %w1, 1b"
+ : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
+ : "r" (&v->counter), "Ir" (i)
+ : "cc");
+}
+
+static inline int atomic_add_return(int i, atomic_t *v)
+{
+ unsigned long tmp;
+ int result;
+
+ asm volatile("// atomic_add_return\n"
+"1: ldaxr %w0, [%3]\n"
+" add %w0, %w0, %w4\n"
+" stlxr %w1, %w0, [%3]\n"
+" cbnz %w1, 1b"
+ : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
+ : "r" (&v->counter), "Ir" (i)
+ : "cc");
+
+ return result;
+}
+
+static inline void atomic_sub(int i, atomic_t *v)
+{
+ unsigned long tmp;
+ int result;
+
+ asm volatile("// atomic_sub\n"
+"1: ldxr %w0, [%3]\n"
+" sub %w0, %w0, %w4\n"
+" stxr %w1, %w0, [%3]\n"
+" cbnz %w1, 1b"
+ : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
+ : "r" (&v->counter), "Ir" (i)
+ : "cc");
+}
+
+static inline int atomic_sub_return(int i, atomic_t *v)
+{
+ unsigned long tmp;
+ int result;
+
+ asm volatile("// atomic_sub_return\n"
+"1: ldaxr %w0, [%3]\n"
+" sub %w0, %w0, %w4\n"
+" stlxr %w1, %w0, [%3]\n"
+" cbnz %w1, 1b"
+ : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
+ : "r" (&v->counter), "Ir" (i)
+ : "cc");
+
+ return result;
+}
+
+static inline int atomic_cmpxchg(atomic_t *ptr, int old, int new)
+{
+ unsigned long tmp;
+ int oldval;
+
+ asm volatile("// atomic_cmpxchg\n"
+"1: ldaxr %w1, [%3]\n"
+" cmp %w1, %w4\n"
+" b.ne 2f\n"
+" stlxr %w0, %w5, [%3]\n"
+" cbnz %w0, 1b\n"
+"2:"
+ : "=&r" (tmp), "=&r" (oldval), "+o" (ptr->counter)
+ : "r" (&ptr->counter), "Ir" (old), "r" (new)
+ : "cc");
+
+ return oldval;
+}
+
+static inline void atomic_clear_mask(unsigned long mask, unsigned long *addr)
+{
+ unsigned long tmp, tmp2;
+
+ asm volatile("// atomic_clear_mask\n"
+"1: ldxr %0, [%3]\n"
+" bic %0, %0, %4\n"
+" stxr %w1, %0, [%3]\n"
+" cbnz %w1, 1b"
+ : "=&r" (tmp), "=&r" (tmp2), "+o" (*addr)
+ : "r" (addr), "Ir" (mask)
+ : "cc");
+}
+
+#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
+
+static inline int __atomic_add_unless(atomic_t *v, int a, int u)
+{
+ int c, old;
+
+ c = atomic_read(v);
+ while (c != u && (old = atomic_cmpxchg((v), c, c + a)) != c)
+ c = old;
+ return c;
+}
+
+#define atomic_inc(v) atomic_add(1, v)
+#define atomic_dec(v) atomic_sub(1, v)
+
+#define atomic_inc_and_test(v) (atomic_add_return(1, v) == 0)
+#define atomic_dec_and_test(v) (atomic_sub_return(1, v) == 0)
+#define atomic_inc_return(v) (atomic_add_return(1, v))
+#define atomic_dec_return(v) (atomic_sub_return(1, v))
+#define atomic_sub_and_test(i, v) (atomic_sub_return(i, v) == 0)
+
+#define atomic_add_negative(i,v) (atomic_add_return(i, v) < 0)
+
+#define smp_mb__before_atomic_dec() smp_mb()
+#define smp_mb__after_atomic_dec() smp_mb()
+#define smp_mb__before_atomic_inc() smp_mb()
+#define smp_mb__after_atomic_inc() smp_mb()
+
+/*
+ * 64-bit atomic operations.
+ */
+#define ATOMIC64_INIT(i) { (i) }
+
+#define atomic64_read(v) (*(volatile long long *)&(v)->counter)
+#define atomic64_set(v,i) (((v)->counter) = (i))
+
+static inline void atomic64_add(u64 i, atomic64_t *v)
+{
+ long result;
+ unsigned long tmp;
+
+ asm volatile("// atomic64_add\n"
+"1: ldxr %0, [%3]\n"
+" add %0, %0, %4\n"
+" stxr %w1, %0, [%3]\n"
+" cbnz %w1, 1b"
+ : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
+ : "r" (&v->counter), "Ir" (i)
+ : "cc");
+}
+
+static inline long atomic64_add_return(long i, atomic64_t *v)
+{
+ long result;
+ unsigned long tmp;
+
+ asm volatile("// atomic64_add_return\n"
+"1: ldaxr %0, [%3]\n"
+" add %0, %0, %4\n"
+" stlxr %w1, %0, [%3]\n"
+" cbnz %w1, 1b"
+ : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
+ : "r" (&v->counter), "Ir" (i)
+ : "cc");
+
+ return result;
+}
+
+static inline void atomic64_sub(u64 i, atomic64_t *v)
+{
+ long result;
+ unsigned long tmp;
+
+ asm volatile("// atomic64_sub\n"
+"1: ldxr %0, [%3]\n"
+" sub %0, %0, %4\n"
+" stxr %w1, %0, [%3]\n"
+" cbnz %w1, 1b"
+ : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
+ : "r" (&v->counter), "Ir" (i)
+ : "cc");
+}
+
+static inline long atomic64_sub_return(long i, atomic64_t *v)
+{
+ long result;
+ unsigned long tmp;
+
+ asm volatile("// atomic64_sub_return\n"
+"1: ldaxr %0, [%3]\n"
+" sub %0, %0, %4\n"
+" stlxr %w1, %0, [%3]\n"
+" cbnz %w1, 1b"
+ : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
+ : "r" (&v->counter), "Ir" (i)
+ : "cc");
+
+ return result;
+}
+
+static inline long atomic64_cmpxchg(atomic64_t *ptr, long old, long new)
+{
+ long oldval;
+ unsigned long res;
+
+ asm volatile("// atomic64_cmpxchg\n"
+"1: ldaxr %1, [%3]\n"
+" cmp %1, %4\n"
+" b.ne 2f\n"
+" stlxr %w0, %5, [%3]\n"
+" cbnz %w0, 1b\n"
+"2:"
+ : "=&r" (res), "=&r" (oldval), "+o" (ptr->counter)
+ : "r" (&ptr->counter), "Ir" (old), "r" (new)
+ : "cc");
+
+ return oldval;
+}
+
+#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))
+
+static inline long atomic64_dec_if_positive(atomic64_t *v)
+{
+ long result;
+ unsigned long tmp;
+
+ asm volatile("// atomic64_dec_if_positive\n"
+"1: ldaxr %0, [%3]\n"
+" subs %0, %0, #1\n"
+" b.mi 2f\n"
+" stlxr %w1, %0, [%3]\n"
+" cbnz %w1, 1b\n"
+"2:"
+ : "=&r" (result), "=&r" (tmp), "+o" (v->counter)
+ : "r" (&v->counter)
+ : "cc");
+
+ return result;
+}
+
+static inline int atomic64_add_unless(atomic64_t *v, long a, long u)
+{
+ long c, old;
+
+ c = atomic64_read(v);
+ while (c != u && (old = atomic64_cmpxchg((v), c, c + a)) != c)
+ c = old;
+
+ return c != u;
+}
+
+#define atomic64_add_negative(a, v) (atomic64_add_return((a), (v)) < 0)
+#define atomic64_inc(v) atomic64_add(1LL, (v))
+#define atomic64_inc_return(v) atomic64_add_return(1LL, (v))
+#define atomic64_inc_and_test(v) (atomic64_inc_return(v) == 0)
+#define atomic64_sub_and_test(a, v) (atomic64_sub_return((a), (v)) == 0)
+#define atomic64_dec(v) atomic64_sub(1LL, (v))
+#define atomic64_dec_return(v) atomic64_sub_return(1LL, (v))
+#define atomic64_dec_and_test(v) (atomic64_dec_return((v)) == 0)
+#define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1LL, 0LL)
+
+#endif
+#endif