From 4d8e2f135d659697337f8d4a33fec60cd475f0dc Mon Sep 17 00:00:00 2001
From: Christoph Muellner <cmuellner@linux.com>
Date: Tue, 6 Apr 2021 03:53:54 +0200
Subject: lib: sbi: Replace test-and-set locks by ticket locks
Replace the test-and-set spinlock implementation with ticket locks
in order to get fairness (in form of FIFO order).
The implementation uses a 32-bit wide struct, which consists of
two 16-bit counters (owner and next). This is inspired by similar
spinlock implementations on other architectures.
This allows that the code works for both, RV32 and RV64.
Signed-off-by: Christoph Muellner <cmuellner@linux.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Xiang W <wxjstz@126.com>
---
include/sbi/riscv_locks.h | 33 ++++++++++++++++++++++-----------
1 file changed, 22 insertions(+), 11 deletions(-)
(limited to 'include')
diff --git a/include/sbi/riscv_locks.h b/include/sbi/riscv_locks.h
index faa9676..492935f 100644
--- a/include/sbi/riscv_locks.h
+++ b/include/sbi/riscv_locks.h
@@ -2,26 +2,37 @@
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2019 Western Digital Corporation or its affiliates.
- *
- * Authors:
- * Anup Patel <anup.patel@wdc.com>
+ * Copyright (c) 2021 Christoph Müllner <cmuellner@linux.com>
*/
#ifndef __RISCV_LOCKS_H__
#define __RISCV_LOCKS_H__
+#include <sbi/sbi_types.h>
+
+#define TICKET_SHIFT 16
+
typedef struct {
- volatile long lock;
-} spinlock_t;
+#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+ u16 next;
+ u16 owner;
+#else
+ u16 owner;
+ u16 next;
+#endif
+} __aligned(4) spinlock_t;
+
+#define __SPIN_LOCK_UNLOCKED \
+ (spinlock_t) { 0, 0 }
-#define __RISCV_SPIN_UNLOCKED 0
+#define SPIN_LOCK_INIT(x) \
+ x = __SPIN_LOCK_UNLOCKED
-#define SPIN_LOCK_INIT(x) (x).lock = __RISCV_SPIN_UNLOCKED
+#define SPIN_LOCK_INITIALIZER \
+ __SPIN_LOCK_UNLOCKED
-#define SPIN_LOCK_INITIALIZER \
- { \
- .lock = __RISCV_SPIN_UNLOCKED, \
- }
+#define DEFINE_SPIN_LOCK(x) \
+ spinlock_t SPIN_LOCK_INIT(x)
int spin_lock_check(spinlock_t *lock);
--
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