[PATCH V3 5/5] riscv: atomic: Add conditional atomic operations' optimization

[guoren at kernel.org]

From: Guo Ren <guoren at linux.alibaba.com>

Add conditional atomic operations' optimization:
 - arch_atomic_inc_unless_negative
 - arch_atomic_dec_unless_positive
 - arch_atomic64_inc_unless_negative
 - arch_atomic64_dec_unless_positive

Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
Signed-off-by: Guo Ren <guoren at kernel.org>
Cc: Palmer Dabbelt <palmer at dabbelt.com>
Cc: Mark Rutland <mark.rutland at arm.com>
Cc: Andrea Parri <parri.andrea at gmail.com>
Cc: Dan Lustig <dlustig at nvidia.com>
---
 arch/riscv/include/asm/atomic.h | 78 +++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)

diff --git a/arch/riscv/include/asm/atomic.h b/arch/riscv/include/asm/atomic.h
index 5589e1de2c80..a62c5de71033 100644
--- a/arch/riscv/include/asm/atomic.h
+++ b/arch/riscv/include/asm/atomic.h
@@ -374,6 +374,44 @@ ATOMIC_OPS()
 #undef ATOMIC_OPS
 #undef ATOMIC_OP
 
+static __always_inline bool arch_atomic_inc_unless_negative(atomic_t *v)
+{
+	int prev, rc;
+
+	__asm__ __volatile__ (
+		"0:	lr.w      %[p],  %[c]\n"
+		"	bltz      %[p],  1f\n"
+		"	addi      %[rc], %[p], 1\n"
+		"	sc.w.aqrl %[rc], %[rc], %[c]\n"
+		"	bnez      %[rc], 0b\n"
+		"1:\n"
+		: [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter)
+		:
+		: "memory");
+	return !(prev < 0);
+}
+
+#define arch_atomic_inc_unless_negative arch_atomic_inc_unless_negative
+
+static __always_inline bool arch_atomic_dec_unless_positive(atomic_t *v)
+{
+	int prev, rc;
+
+	__asm__ __volatile__ (
+		"0:	lr.w      %[p],  %[c]\n"
+		"	bgtz      %[p],  1f\n"
+		"	addi      %[rc], %[p], -1\n"
+		"	sc.w.aqrl %[rc], %[rc], %[c]\n"
+		"	bnez      %[rc], 0b\n"
+		"1:\n"
+		: [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter)
+		:
+		: "memory");
+	return !(prev > 0);
+}
+
+#define arch_atomic_dec_unless_positive arch_atomic_dec_unless_positive
+
 static __always_inline int arch_atomic_dec_if_positive(atomic_t *v)
 {
        int prev, rc;
@@ -394,6 +432,46 @@ static __always_inline int arch_atomic_dec_if_positive(atomic_t *v)
 #define arch_atomic_dec_if_positive arch_atomic_dec_if_positive
 
 #ifndef CONFIG_GENERIC_ATOMIC64
+static __always_inline bool arch_atomic64_inc_unless_negative(atomic64_t *v)
+{
+	s64 prev;
+	long rc;
+
+	__asm__ __volatile__ (
+		"0:	lr.d      %[p],  %[c]\n"
+		"	bltz      %[p],  1f\n"
+		"	addi      %[rc], %[p], 1\n"
+		"	sc.d.aqrl %[rc], %[rc], %[c]\n"
+		"	bnez      %[rc], 0b\n"
+		"1:\n"
+		: [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter)
+		:
+		: "memory");
+	return !(prev < 0);
+}
+
+#define arch_atomic64_inc_unless_negative arch_atomic64_inc_unless_negative
+
+static __always_inline bool arch_atomic64_dec_unless_positive(atomic64_t *v)
+{
+	s64 prev;
+	long rc;
+
+	__asm__ __volatile__ (
+		"0:	lr.d      %[p],  %[c]\n"
+		"	bgtz      %[p],  1f\n"
+		"	addi      %[rc], %[p], -1\n"
+		"	sc.d.aqrl %[rc], %[rc], %[c]\n"
+		"	bnez      %[rc], 0b\n"
+		"1:\n"
+		: [p]"=&r" (prev), [rc]"=&r" (rc), [c]"+A" (v->counter)
+		:
+		: "memory");
+	return !(prev > 0);
+}
+
+#define arch_atomic64_dec_unless_positive arch_atomic64_dec_unless_positive
+
 static __always_inline s64 arch_atomic64_dec_if_positive(atomic64_t *v)
 {
        s64 prev;
-- 
2.25.1