[PATCH 12/17] riscv: Implement xor_unlock_is_negative_byte

Matthew Wilcox (Oracle)
2023-09-15T18:38:16Z

Inspired by the riscv clear_bit_unlock(), this will surely be
more efficient than the generic one defined in filemap.c.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
arch/riscv/include/asm/bitops.h | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/arch/riscv/include/asm/bitops.h b/arch/riscv/include/asm/bitops.h
index 3540b690944b..15e3044298a2 100644
--- a/arch/riscv/include/asm/bitops.h
+++ b/arch/riscv/include/asm/bitops.h
@@ -191,6 +191,19 @@ static inline void __clear_bit_unlock(
clear_bit_unlock(nr, addr);
}

+static inline bool xor_unlock_is_negative_byte(unsigned long mask,
+ volatile unsigned long *addr)
+{
+ unsigned long res;
+ __asm__ __volatile__ (
+ __AMO(xor) ".rl %0, %2, %1"
+ : "=r" (res), "+A" (*addr)
+ : "r" (__NOP(mask))
+ : "memory");
+ return (res & BIT(7)) != 0;
+}
+#define xor_unlock_is_negative_byte xor_unlock_is_negative_byte
+
#undef __test_and_op_bit
#undef __op_bit
#undef __NOP
--
2.40.1