# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1229183776 0
# Node ID 6a3c2b4459ade54bb860d36b7566b182f4ec1cf9
# Parent e767f80d4bcc90d761df14ba89c2d72d44c99d8b
x86: Clean up and simplify rwlock implementation.
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
xen/arch/x86/rwlock.c | 28 ----------------
xen/include/asm-x86/rwlock.h | 71 -----------------------------------------
xen/arch/x86/Makefile | 1
xen/include/asm-x86/spinlock.h | 49 +++++++++++++++++++---------
4 files changed, 34 insertions(+), 115 deletions(-)
diff -r e767f80d4bcc -r 6a3c2b4459ad xen/arch/x86/Makefile
--- a/xen/arch/x86/Makefile Sat Dec 13 15:28:10 2008 +0000
+++ b/xen/arch/x86/Makefile Sat Dec 13 15:56:16 2008 +0000
@@ -37,7 +37,6 @@ obj-y += numa.o
obj-y += numa.o
obj-y += pci.o
obj-y += physdev.o
-obj-y += rwlock.o
obj-y += setup.o
obj-y += shutdown.o
obj-y += smp.o
diff -r e767f80d4bcc -r 6a3c2b4459ad xen/arch/x86/rwlock.c
--- a/xen/arch/x86/rwlock.c Sat Dec 13 15:28:10 2008 +0000
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,28 +0,0 @@
-#include <asm/atomic.h>
-#include <asm/rwlock.h>
-
-#if defined(CONFIG_SMP)
-asm(
-".align 4\n"
-".globl __write_lock_failed\n"
-"__write_lock_failed:\n"
-" " LOCK "addl $" RW_LOCK_BIAS_STR ",(%"__OP"ax)\n"
-"1: rep; nop\n"
-" cmpl $" RW_LOCK_BIAS_STR ",(%"__OP"ax)\n"
-" jne 1b\n"
-" " LOCK "subl $" RW_LOCK_BIAS_STR ",(%"__OP"ax)\n"
-" jnz __write_lock_failed\n"
-" ret\n"
-
-".align 4\n"
-".globl __read_lock_failed\n"
-"__read_lock_failed:\n"
-" lock ; incl (%"__OP"ax)\n"
-"1: rep; nop\n"
-" cmpl $1,(%"__OP"ax)\n"
-" js 1b\n"
-" lock ; decl (%"__OP"ax)\n"
-" js __read_lock_failed\n"
-" ret\n"
-);
-#endif
diff -r e767f80d4bcc -r 6a3c2b4459ad xen/include/asm-x86/rwlock.h
--- a/xen/include/asm-x86/rwlock.h Sat Dec 13 15:28:10 2008 +0000
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,71 +0,0 @@
-/* include/asm-x86/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.
- *
- * 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_RWLOCK_H
-#define _ASM_X86_RWLOCK_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" \
- "jns 1f\n\t" \
- "call " helper "\n\t" \
- "1:\n" \
- ::"a" (rw) : "memory")
-
-#define __build_read_lock_const(rw, helper) \
- asm volatile(LOCK "subl $1,%0\n\t" \
- "jns 1f\n\t" \
- "push %%"__OP"ax\n\t" \
- "lea %0,%%"__OP"ax\n\t" \
- "call " helper "\n\t" \
- "pop %%"__OP"ax\n\t" \
- "1:\n" \
- :"=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" \
- "jz 1f\n\t" \
- "call " helper "\n\t" \
- "1:\n" \
- ::"a" (rw) : "memory")
-
-#define __build_write_lock_const(rw, helper) \
- asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
- "jz 1f\n\t" \
- "push %%"__OP"ax\n\t" \
- "lea %0,%%"__OP"ax\n\t" \
- "call " helper "\n\t" \
- "pop %%"__OP"ax\n\t" \
- "1:\n" \
- :"=m" (*(volatile int *)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
diff -r e767f80d4bcc -r 6a3c2b4459ad xen/include/asm-x86/spinlock.h
--- a/xen/include/asm-x86/spinlock.h Sat Dec 13 15:28:10 2008 +0000
+++ b/xen/include/asm-x86/spinlock.h Sat Dec 13 15:56:16 2008 +0000
@@ -4,7 +4,6 @@
#include <xen/config.h>
#include <xen/lib.h>
#include <asm/atomic.h>
-#include <asm/rwlock.h>
typedef struct {
volatile s16 lock;
@@ -49,30 +48,50 @@ typedef struct {
volatile unsigned int lock;
} raw_rwlock_t;
+#define RW_LOCK_BIAS 0x01000000
#define _RAW_RW_LOCK_UNLOCKED /*(raw_rwlock_t)*/ { RW_LOCK_BIAS }
-/*
- * On x86, we implement read-write locks as a 32-bit counter
- * with the high bit (sign) being the "contended" bit.
- */
static always_inline void _raw_read_lock(raw_rwlock_t *rw)
{
- __build_read_lock(rw, "__read_lock_failed");
+ asm volatile (
+ "1: lock; decl %0 \n"
+ " jns 3f \n"
+ " lock; incl %0 \n"
+ "2: rep; nop \n"
+ " cmpl $1,%0 \n"
+ " js 2b \n"
+ " jmp 1b \n"
+ "3:"
+ : "=m" (rw->lock) : : "memory" );
}
static always_inline void _raw_write_lock(raw_rwlock_t *rw)
{
- __build_write_lock(rw, "__write_lock_failed");
+ asm volatile (
+ "1: lock; subl %1,%0 \n"
+ " jz 3f \n"
+ " lock; addl %1,%0 \n"
+ "2: rep; nop \n"
+ " cmpl %1,%0 \n"
+ " jne 2b \n"
+ " jmp 1b \n"
+ "3:"
+ : "=m" (rw->lock) : "i" (RW_LOCK_BIAS) : "memory" );
}
-#define _raw_read_unlock(rw) \
- asm volatile ( \
- "lock ; incl %0" : \
- "=m" ((rw)->lock) : : "memory" )
-#define _raw_write_unlock(rw) \
- asm volatile ( \
- "lock ; addl $" RW_LOCK_BIAS_STR ",%0" : \
- "=m" ((rw)->lock) : : "memory" )
+static always_inline void _raw_read_unlock(raw_rwlock_t *rw)
+{
+ asm volatile (
+ "lock ; incl %0"
+ : "=m" ((rw)->lock) : : "memory" );
+}
+
+static always_inline void _raw_write_unlock(raw_rwlock_t *rw)
+{
+ asm volatile (
+ "lock ; addl %1,%0"
+ : "=m" ((rw)->lock) : "i" (RW_LOCK_BIAS) : "memory" );
+}
#define _raw_rw_is_locked(x) ((x)->lock < RW_LOCK_BIAS)
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