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Date: Fri, 18 Jan 2013 17:54:25 +0530
From: Vineet Gupta <Vineet.Gupta1@...opsys.com>
To: <linux-arch@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <arnd@...db.de>, Vineet Gupta <Vineet.Gupta1@...opsys.com>
Subject: [PATCH v2 11/76] ARC: Spinlock/rwlock/mutex primitives
Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
---
arch/arc/include/asm/mutex.h | 9 ++
arch/arc/include/asm/spinlock.h | 144 +++++++++++++++++++++++++++++++++
arch/arc/include/asm/spinlock_types.h | 35 ++++++++
3 files changed, 188 insertions(+), 0 deletions(-)
create mode 100644 arch/arc/include/asm/mutex.h
create mode 100644 arch/arc/include/asm/spinlock.h
create mode 100644 arch/arc/include/asm/spinlock_types.h
diff --git a/arch/arc/include/asm/mutex.h b/arch/arc/include/asm/mutex.h
new file mode 100644
index 0000000..3be5e64
--- /dev/null
+++ b/arch/arc/include/asm/mutex.h
@@ -0,0 +1,9 @@
+/*
+ * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ * 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.
+ */
+
+#include <asm-generic/mutex-xchg.h>
diff --git a/arch/arc/include/asm/spinlock.h b/arch/arc/include/asm/spinlock.h
new file mode 100644
index 0000000..f158197
--- /dev/null
+++ b/arch/arc/include/asm/spinlock.h
@@ -0,0 +1,144 @@
+/*
+ * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ * 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.
+ */
+
+#ifndef __ASM_SPINLOCK_H
+#define __ASM_SPINLOCK_H
+
+#include <asm/spinlock_types.h>
+#include <asm/processor.h>
+#include <asm/barrier.h>
+
+#define arch_spin_is_locked(x) ((x)->slock != __ARCH_SPIN_LOCK_UNLOCKED__)
+#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
+#define arch_spin_unlock_wait(x) \
+ do { while (arch_spin_is_locked(x)) cpu_relax(); } while (0)
+
+static inline void arch_spin_lock(arch_spinlock_t *lock)
+{
+ unsigned int tmp = __ARCH_SPIN_LOCK_LOCKED__;
+
+ __asm__ __volatile__(
+ "1: ex %0, [%1] \n"
+ " breq %0, %2, 1b \n"
+ : "+&r" (tmp)
+ : "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__)
+ : "memory");
+}
+
+static inline int arch_spin_trylock(arch_spinlock_t *lock)
+{
+ unsigned int tmp = __ARCH_SPIN_LOCK_LOCKED__;
+
+ __asm__ __volatile__(
+ "1: ex %0, [%1] \n"
+ : "+r" (tmp)
+ : "r"(&(lock->slock))
+ : "memory");
+
+ return (tmp == __ARCH_SPIN_LOCK_UNLOCKED__);
+}
+
+static inline void arch_spin_unlock(arch_spinlock_t *lock)
+{
+ lock->slock = __ARCH_SPIN_LOCK_UNLOCKED__;
+ smp_mb();
+}
+
+/*
+ * Read-write spinlocks, allowing multiple readers but only one writer.
+ *
+ * The spinlock itself is contained in @counter and access to it is
+ * serialized with @lock_mutex.
+ *
+ * Unfair locking as Writers could be starved indefinitely by Reader(s)
+ */
+
+/* Would read_trylock() succeed? */
+#define arch_read_can_lock(x) ((x)->counter > 0)
+
+/* Would write_trylock() succeed? */
+#define arch_write_can_lock(x) ((x)->counter == __ARCH_RW_LOCK_UNLOCKED__)
+
+/* 1 - lock taken successfully */
+static inline int arch_read_trylock(arch_rwlock_t *rw)
+{
+ int ret = 0;
+
+ arch_spin_lock(&(rw->lock_mutex));
+
+ /*
+ * zero means writer holds the lock exclusively, deny Reader.
+ * Otherwise grant lock to first/subseq reader
+ */
+ if (rw->counter > 0) {
+ rw->counter--;
+ ret = 1;
+ }
+
+ arch_spin_unlock(&(rw->lock_mutex));
+
+ smp_mb();
+ return ret;
+}
+
+/* 1 - lock taken successfully */
+static inline int arch_write_trylock(arch_rwlock_t *rw)
+{
+ int ret = 0;
+
+ arch_spin_lock(&(rw->lock_mutex));
+
+ /*
+ * If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
+ * deny writer. Otherwise if unlocked grant to writer
+ * Hence the claim that Linux rwlocks are unfair to writers.
+ * (can be starved for an indefinite time by readers).
+ */
+ if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
+ rw->counter = 0;
+ ret = 1;
+ }
+ arch_spin_unlock(&(rw->lock_mutex));
+
+ return ret;
+}
+
+static inline void arch_read_lock(arch_rwlock_t *rw)
+{
+ while (!arch_read_trylock(rw))
+ cpu_relax();
+}
+
+static inline void arch_write_lock(arch_rwlock_t *rw)
+{
+ while (!arch_write_trylock(rw))
+ cpu_relax();
+}
+
+static inline void arch_read_unlock(arch_rwlock_t *rw)
+{
+ arch_spin_lock(&(rw->lock_mutex));
+ rw->counter++;
+ arch_spin_unlock(&(rw->lock_mutex));
+}
+
+static inline void arch_write_unlock(arch_rwlock_t *rw)
+{
+ arch_spin_lock(&(rw->lock_mutex));
+ rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
+ arch_spin_unlock(&(rw->lock_mutex));
+}
+
+#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
+#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
+
+#define arch_spin_relax(lock) cpu_relax()
+#define arch_read_relax(lock) cpu_relax()
+#define arch_write_relax(lock) cpu_relax()
+
+#endif /* __ASM_SPINLOCK_H */
diff --git a/arch/arc/include/asm/spinlock_types.h b/arch/arc/include/asm/spinlock_types.h
new file mode 100644
index 0000000..8276bfd
--- /dev/null
+++ b/arch/arc/include/asm/spinlock_types.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ * 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.
+ */
+
+#ifndef __ASM_SPINLOCK_TYPES_H
+#define __ASM_SPINLOCK_TYPES_H
+
+typedef struct {
+ volatile unsigned int slock;
+} arch_spinlock_t;
+
+#define __ARCH_SPIN_LOCK_UNLOCKED__ 0
+#define __ARCH_SPIN_LOCK_LOCKED__ 1
+
+#define __ARCH_SPIN_LOCK_UNLOCKED { __ARCH_SPIN_LOCK_UNLOCKED__ }
+#define __ARCH_SPIN_LOCK_LOCKED { __ARCH_SPIN_LOCK_LOCKED__ }
+
+/*
+ * Unlocked: 0x01_00_00_00
+ * Read lock(s): 0x00_FF_00_00 to say 0x01
+ * Write lock: 0x0, but only possible if prior value "unlocked" 0x0100_0000
+ */
+typedef struct {
+ volatile unsigned int counter;
+ arch_spinlock_t lock_mutex;
+} arch_rwlock_t;
+
+#define __ARCH_RW_LOCK_UNLOCKED__ 0x01000000
+#define __ARCH_RW_LOCK_UNLOCKED { .counter = __ARCH_RW_LOCK_UNLOCKED__ }
+
+#endif
--
1.7.4.1
--
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