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Diffstat (limited to 'include/asm-x86_64/rwlock.h')
-rw-r--r--include/asm-x86_64/rwlock.h86
1 files changed, 86 insertions, 0 deletions
diff --git a/include/asm-x86_64/rwlock.h b/include/asm-x86_64/rwlock.h
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+++ b/include/asm-x86_64/rwlock.h
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+/* include/asm-x86_64/rwlock.h
+ *
+ * Helpers used by both rw spinlocks and rw semaphores.
+ *
+ * Based in part on code from semaphore.h and
+ * spinlock.h Copyright 1996 Linus Torvalds.
+ *
+ * Copyright 1999 Red Hat, Inc.
+ * Copyright 2001,2002 SuSE labs
+ *
+ * Written by Benjamin LaHaise.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+#ifndef _ASM_X86_64_RWLOCK_H
+#define _ASM_X86_64_RWLOCK_H
+
+#include <linux/stringify.h>
+
+#define RW_LOCK_BIAS 0x01000000
+#define RW_LOCK_BIAS_STR "0x01000000"
+
+#define __build_read_lock_ptr(rw, helper) \
+ asm volatile(LOCK "subl $1,(%0)\n\t" \
+ "js 2f\n" \
+ "1:\n" \
+ LOCK_SECTION_START("") \
+ "2:\tcall " helper "\n\t" \
+ "jmp 1b\n" \
+ LOCK_SECTION_END \
+ ::"a" (rw) : "memory")
+
+#define __build_read_lock_const(rw, helper) \
+ asm volatile(LOCK "subl $1,%0\n\t" \
+ "js 2f\n" \
+ "1:\n" \
+ LOCK_SECTION_START("") \
+ "2:\tpushq %%rax\n\t" \
+ "leaq %0,%%rax\n\t" \
+ "call " helper "\n\t" \
+ "popq %%rax\n\t" \
+ "jmp 1b\n" \
+ LOCK_SECTION_END \
+ :"=m" (*((volatile int *)rw))::"memory")
+
+#define __build_read_lock(rw, helper) do { \
+ if (__builtin_constant_p(rw)) \
+ __build_read_lock_const(rw, helper); \
+ else \
+ __build_read_lock_ptr(rw, helper); \
+ } while (0)
+
+#define __build_write_lock_ptr(rw, helper) \
+ asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
+ "jnz 2f\n" \
+ "1:\n" \
+ LOCK_SECTION_START("") \
+ "2:\tcall " helper "\n\t" \
+ "jmp 1b\n" \
+ LOCK_SECTION_END \
+ ::"a" (rw) : "memory")
+
+#define __build_write_lock_const(rw, helper) \
+ asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
+ "jnz 2f\n" \
+ "1:\n" \
+ LOCK_SECTION_START("") \
+ "2:\tpushq %%rax\n\t" \
+ "leaq %0,%%rax\n\t" \
+ "call " helper "\n\t" \
+ "popq %%rax\n\t" \
+ "jmp 1b\n" \
+ LOCK_SECTION_END \
+ :"=m" (*((volatile long *)rw))::"memory")
+
+#define __build_write_lock(rw, helper) do { \
+ if (__builtin_constant_p(rw)) \
+ __build_write_lock_const(rw, helper); \
+ else \
+ __build_write_lock_ptr(rw, helper); \
+ } while (0)
+
+#endif