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[v2,12/17] riscv: Implement xor_unlock_is_negative_byte

Message ID 20231004165317.1061855-13-willy@infradead.org (mailing list archive)
State New
Headers show
Series Add folio_end_read | expand

Commit Message

Matthew Wilcox (Oracle) Oct. 4, 2023, 4:53 p.m. UTC 
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(+)
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Patch

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