[PATCH 4/5] atomic: dec_and_lock use cmpxchg
From: Nick Piggin
Date: Wed Sep 14 2005 - 10:06:30 EST
I noticed David posted a patch to do something similar the
other day. With a generic atomic_cmpxchg available, such a
patch is no longer objectionable to those architectures
that don't #define __HAVE_ARCH_CMPXCHG
Do we want this David? Any other architecture have a super
optimised atomic_dec_and_lock that surpasses this
implementation?
--
SUSE Labs, Novell Inc.
Index: linux-2.6/lib/dec_and_lock.c
===================================================================
--- linux-2.6.orig/lib/dec_and_lock.c
+++ linux-2.6/lib/dec_and_lock.c
@@ -3,10 +3,21 @@
#include <asm/atomic.h>
/*
- * This is an architecture-neutral, but slow,
- * implementation of the notion of "decrement
- * a reference count, and return locked if it
- * decremented to zero".
+ * Decrement v if it is not equal to one, and return non zero.
+ * Otherwise return zero.
+ */
+static int atomic_dec_not_one(atomic_t *v)
+{
+ int c, old;
+ c = atomic_read(v);
+ while (c > 1 && (old = atomic_cmpxchg((v), c, c - 1)) != c)
+ c = old;
+ return c > 1;
+}
+
+/*
+ * Implement an atomic "decrement a reference count, and
+ * return locked if it decremented to zero" operation.
*
* NOTE NOTE NOTE! This is _not_ equivalent to
*
@@ -19,14 +30,16 @@
* because the spin-lock and the decrement must be
* "atomic".
*
- * This slow version gets the spinlock unconditionally,
- * and releases it if it isn't needed. Architectures
- * are encouraged to come up with better approaches,
- * this is trivially done efficiently using a load-locked
- * store-conditional approach, for example.
+ * This version shortcuts the unconditional spin lock on
+ * CONFIG_SMP builds to avoid the expensive lock operation.
*/
int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
{
+#ifdef CONFIG_SMP
+ if (atomic_dec_not_one(atomic))
+ return 0;
+#endif
+
spin_lock(lock);
if (atomic_dec_and_test(atomic))
return 1;
Index: linux-2.6/arch/alpha/lib/dec_and_lock.c
===================================================================
--- linux-2.6.orig/arch/alpha/lib/dec_and_lock.c
+++ /dev/null
@@ -1,42 +0,0 @@
-/*
- * arch/alpha/lib/dec_and_lock.c
- *
- * ll/sc version of atomic_dec_and_lock()
- *
- */
-
-#include <linux/spinlock.h>
-#include <asm/atomic.h>
-
- asm (".text \n\
- .global _atomic_dec_and_lock \n\
- .ent _atomic_dec_and_lock \n\
- .align 4 \n\
-_atomic_dec_and_lock: \n\
- .prologue 0 \n\
-1: ldl_l $1, 0($16) \n\
- subl $1, 1, $1 \n\
- beq $1, 2f \n\
- stl_c $1, 0($16) \n\
- beq $1, 4f \n\
- mb \n\
- clr $0 \n\
- ret \n\
-2: br $29, 3f \n\
-3: ldgp $29, 0($29) \n\
- br $atomic_dec_and_lock_1..ng \n\
- .subsection 2 \n\
-4: br 1b \n\
- .previous \n\
- .end _atomic_dec_and_lock");
-
-static int __attribute_used__
-atomic_dec_and_lock_1(atomic_t *atomic, spinlock_t *lock)
-{
- /* Slow path */
- spin_lock(lock);
- if (atomic_dec_and_test(atomic))
- return 1;
- spin_unlock(lock);
- return 0;
-}
Index: linux-2.6/arch/i386/lib/dec_and_lock.c
===================================================================
--- linux-2.6.orig/arch/i386/lib/dec_and_lock.c
+++ /dev/null
@@ -1,42 +0,0 @@
-/*
- * x86 version of "atomic_dec_and_lock()" using
- * the atomic "cmpxchg" instruction.
- *
- * (For CPU's lacking cmpxchg, we use the slow
- * generic version, and this one never even gets
- * compiled).
- */
-
-#include <linux/spinlock.h>
-#include <linux/module.h>
-#include <asm/atomic.h>
-
-int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
-{
- int counter;
- int newcount;
-
-repeat:
- counter = atomic_read(atomic);
- newcount = counter-1;
-
- if (!newcount)
- goto slow_path;
-
- asm volatile("lock; cmpxchgl %1,%2"
- :"=a" (newcount)
- :"r" (newcount), "m" (atomic->counter), "0" (counter));
-
- /* If the above failed, "eax" will have changed */
- if (newcount != counter)
- goto repeat;
- return 0;
-
-slow_path:
- spin_lock(lock);
- if (atomic_dec_and_test(atomic))
- return 1;
- spin_unlock(lock);
- return 0;
-}
-EXPORT_SYMBOL(_atomic_dec_and_lock);
Index: linux-2.6/arch/ia64/lib/dec_and_lock.c
===================================================================
--- linux-2.6.orig/arch/ia64/lib/dec_and_lock.c
+++ /dev/null
@@ -1,42 +0,0 @@
-/*
- * Copyright (C) 2003 Jerome Marchand, Bull S.A.
- * Cleaned up by David Mosberger-Tang <davidm@xxxxxxxxxx>
- *
- * This file is released under the GPLv2, or at your option any later version.
- *
- * ia64 version of "atomic_dec_and_lock()" using the atomic "cmpxchg" instruction. This
- * code is an adaptation of the x86 version of "atomic_dec_and_lock()".
- */
-
-#include <linux/compiler.h>
-#include <linux/module.h>
-#include <linux/spinlock.h>
-#include <asm/atomic.h>
-
-/*
- * Decrement REFCOUNT and if the count reaches zero, acquire the spinlock. Both of these
- * operations have to be done atomically, so that the count doesn't drop to zero without
- * acquiring the spinlock first.
- */
-int
-_atomic_dec_and_lock (atomic_t *refcount, spinlock_t *lock)
-{
- int old, new;
-
- do {
- old = atomic_read(refcount);
- new = old - 1;
-
- if (unlikely (old == 1)) {
- /* oops, we may be decrementing to zero, do it the slow way... */
- spin_lock(lock);
- if (atomic_dec_and_test(refcount))
- return 1;
- spin_unlock(lock);
- return 0;
- }
- } while (cmpxchg(&refcount->counter, old, new) != old);
- return 0;
-}
-
-EXPORT_SYMBOL(_atomic_dec_and_lock);
Index: linux-2.6/arch/mips/lib/dec_and_lock.c
===================================================================
--- linux-2.6.orig/arch/mips/lib/dec_and_lock.c
+++ /dev/null
@@ -1,47 +0,0 @@
-/*
- * MIPS version of atomic_dec_and_lock() using cmpxchg
- *
- * 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.
- */
-
-#include <linux/module.h>
-#include <linux/spinlock.h>
-#include <asm/atomic.h>
-#include <asm/system.h>
-
-/*
- * This is an implementation of the notion of "decrement a
- * reference count, and return locked if it decremented to zero".
- *
- * This implementation can be used on any architecture that
- * has a cmpxchg, and where atomic->value is an int holding
- * the value of the atomic (i.e. the high bits aren't used
- * for a lock or anything like that).
- */
-int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
-{
- int counter;
- int newcount;
-
- for (;;) {
- counter = atomic_read(atomic);
- newcount = counter - 1;
- if (!newcount)
- break; /* do it the slow way */
-
- newcount = cmpxchg(&atomic->counter, counter, newcount);
- if (newcount == counter)
- return 0;
- }
-
- spin_lock(lock);
- if (atomic_dec_and_test(atomic))
- return 1;
- spin_unlock(lock);
- return 0;
-}
-
-EXPORT_SYMBOL(_atomic_dec_and_lock);
Index: linux-2.6/arch/ppc/lib/dec_and_lock.c
===================================================================
--- linux-2.6.orig/arch/ppc/lib/dec_and_lock.c
+++ /dev/null
@@ -1,38 +0,0 @@
-#include <linux/module.h>
-#include <linux/spinlock.h>
-#include <asm/atomic.h>
-#include <asm/system.h>
-
-/*
- * This is an implementation of the notion of "decrement a
- * reference count, and return locked if it decremented to zero".
- *
- * This implementation can be used on any architecture that
- * has a cmpxchg, and where atomic->value is an int holding
- * the value of the atomic (i.e. the high bits aren't used
- * for a lock or anything like that).
- */
-int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
-{
- int counter;
- int newcount;
-
- for (;;) {
- counter = atomic_read(atomic);
- newcount = counter - 1;
- if (!newcount)
- break; /* do it the slow way */
-
- newcount = cmpxchg(&atomic->counter, counter, newcount);
- if (newcount == counter)
- return 0;
- }
-
- spin_lock(lock);
- if (atomic_dec_and_test(atomic))
- return 1;
- spin_unlock(lock);
- return 0;
-}
-
-EXPORT_SYMBOL(_atomic_dec_and_lock);
Index: linux-2.6/arch/ppc64/lib/dec_and_lock.c
===================================================================
--- linux-2.6.orig/arch/ppc64/lib/dec_and_lock.c
+++ /dev/null
@@ -1,47 +0,0 @@
-/*
- * ppc64 version of atomic_dec_and_lock() using cmpxchg
- *
- * 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.
- */
-
-#include <linux/module.h>
-#include <linux/spinlock.h>
-#include <asm/atomic.h>
-#include <asm/system.h>
-
-/*
- * This is an implementation of the notion of "decrement a
- * reference count, and return locked if it decremented to zero".
- *
- * This implementation can be used on any architecture that
- * has a cmpxchg, and where atomic->value is an int holding
- * the value of the atomic (i.e. the high bits aren't used
- * for a lock or anything like that).
- */
-int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
-{
- int counter;
- int newcount;
-
- for (;;) {
- counter = atomic_read(atomic);
- newcount = counter - 1;
- if (!newcount)
- break; /* do it the slow way */
-
- newcount = cmpxchg(&atomic->counter, counter, newcount);
- if (newcount == counter)
- return 0;
- }
-
- spin_lock(lock);
- if (atomic_dec_and_test(atomic))
- return 1;
- spin_unlock(lock);
- return 0;
-}
-
-EXPORT_SYMBOL(_atomic_dec_and_lock);
Index: linux-2.6/arch/x86_64/lib/dec_and_lock.c
===================================================================
--- linux-2.6.orig/arch/x86_64/lib/dec_and_lock.c
+++ /dev/null
@@ -1,40 +0,0 @@
-/*
- * x86 version of "atomic_dec_and_lock()" using
- * the atomic "cmpxchg" instruction.
- *
- * (For CPU's lacking cmpxchg, we use the slow
- * generic version, and this one never even gets
- * compiled).
- */
-
-#include <linux/spinlock.h>
-#include <asm/atomic.h>
-
-int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
-{
- int counter;
- int newcount;
-
-repeat:
- counter = atomic_read(atomic);
- newcount = counter-1;
-
- if (!newcount)
- goto slow_path;
-
- asm volatile("lock; cmpxchgl %1,%2"
- :"=a" (newcount)
- :"r" (newcount), "m" (atomic->counter), "0" (counter));
-
- /* If the above failed, "eax" will have changed */
- if (newcount != counter)
- goto repeat;
- return 0;
-
-slow_path:
- spin_lock(lock);
- if (atomic_dec_and_test(atomic))
- return 1;
- spin_unlock(lock);
- return 0;
-}
Index: linux-2.6/lib/Makefile
===================================================================
--- linux-2.6.orig/lib/Makefile
+++ linux-2.6/lib/Makefile
@@ -5,7 +5,7 @@
lib-y := errno.o ctype.o string.o vsprintf.o cmdline.o \
bust_spinlocks.o rbtree.o radix-tree.o dump_stack.o \
idr.o div64.o int_sqrt.o bitmap.o extable.o prio_tree.o \
- sha1.o
+ sha1.o dec_and_lock.o
lib-y += kobject.o kref.o kobject_uevent.o klist.o
@@ -24,10 +24,6 @@ lib-$(CONFIG_GENERIC_FIND_NEXT_BIT) += f
obj-$(CONFIG_LOCK_KERNEL) += kernel_lock.o
obj-$(CONFIG_DEBUG_PREEMPT) += smp_processor_id.o
-ifneq ($(CONFIG_HAVE_DEC_LOCK),y)
- lib-y += dec_and_lock.o
-endif
-
obj-$(CONFIG_CRC_CCITT) += crc-ccitt.o
obj-$(CONFIG_CRC16) += crc16.o
obj-$(CONFIG_CRC32) += crc32.o
Index: linux-2.6/arch/alpha/Kconfig
===================================================================
--- linux-2.6.orig/arch/alpha/Kconfig
+++ linux-2.6/arch/alpha/Kconfig
@@ -501,11 +501,6 @@ config SMP
If you don't know what to do here, say N.
-config HAVE_DEC_LOCK
- bool
- depends on SMP
- default y
-
config NR_CPUS
int "Maximum number of CPUs (2-64)"
range 2 64
Index: linux-2.6/arch/i386/Kconfig
===================================================================
--- linux-2.6.orig/arch/i386/Kconfig
+++ linux-2.6/arch/i386/Kconfig
@@ -908,11 +908,6 @@ config IRQBALANCE
The default yes will allow the kernel to do irq load balancing.
Saying no will keep the kernel from doing irq load balancing.
-config HAVE_DEC_LOCK
- bool
- depends on (SMP || PREEMPT) && X86_CMPXCHG
- default y
-
# turning this on wastes a bunch of space.
# Summit needs it only when NUMA is on
config BOOT_IOREMAP
Index: linux-2.6/arch/i386/lib/Makefile
===================================================================
--- linux-2.6.orig/arch/i386/lib/Makefile
+++ linux-2.6/arch/i386/lib/Makefile
@@ -7,4 +7,3 @@ lib-y = checksum.o delay.o usercopy.o ge
bitops.o
lib-$(CONFIG_X86_USE_3DNOW) += mmx.o
-lib-$(CONFIG_HAVE_DEC_LOCK) += dec_and_lock.o
Index: linux-2.6/arch/ia64/Kconfig
===================================================================
--- linux-2.6.orig/arch/ia64/Kconfig
+++ linux-2.6/arch/ia64/Kconfig
@@ -298,11 +298,6 @@ config PREEMPT
source "mm/Kconfig"
-config HAVE_DEC_LOCK
- bool
- depends on (SMP || PREEMPT)
- default y
-
config IA32_SUPPORT
bool "Support for Linux/x86 binaries"
help
Index: linux-2.6/arch/ia64/lib/Makefile
===================================================================
--- linux-2.6.orig/arch/ia64/lib/Makefile
+++ linux-2.6/arch/ia64/lib/Makefile
@@ -15,7 +15,6 @@ lib-$(CONFIG_ITANIUM) += copy_page.o cop
lib-$(CONFIG_MCKINLEY) += copy_page_mck.o memcpy_mck.o
lib-$(CONFIG_PERFMON) += carta_random.o
lib-$(CONFIG_MD_RAID5) += xor.o
-lib-$(CONFIG_HAVE_DEC_LOCK) += dec_and_lock.o
AFLAGS___divdi3.o =
AFLAGS___udivdi3.o = -DUNSIGNED
Index: linux-2.6/arch/m32r/Kconfig
===================================================================
--- linux-2.6.orig/arch/m32r/Kconfig
+++ linux-2.6/arch/m32r/Kconfig
@@ -220,11 +220,6 @@ config PREEMPT
Say Y here if you are building a kernel for a desktop, embedded
or real-time system. Say N if you are unsure.
-config HAVE_DEC_LOCK
- bool
- depends on (SMP || PREEMPT)
- default n
-
config SMP
bool "Symmetric multi-processing support"
---help---
Index: linux-2.6/arch/mips/Kconfig
===================================================================
--- linux-2.6.orig/arch/mips/Kconfig
+++ linux-2.6/arch/mips/Kconfig
@@ -1009,10 +1009,6 @@ config GENERIC_CALIBRATE_DELAY
bool
default y
-config HAVE_DEC_LOCK
- bool
- default y
-
#
# Select some configuration options automatically based on user selections.
#
Index: linux-2.6/arch/ppc/Kconfig
===================================================================
--- linux-2.6.orig/arch/ppc/Kconfig
+++ linux-2.6/arch/ppc/Kconfig
@@ -26,10 +26,6 @@ config GENERIC_CALIBRATE_DELAY
bool
default y
-config HAVE_DEC_LOCK
- bool
- default y
-
config PPC
bool
default y
Index: linux-2.6/arch/ppc64/Kconfig
===================================================================
--- linux-2.6.orig/arch/ppc64/Kconfig
+++ linux-2.6/arch/ppc64/Kconfig
@@ -28,10 +28,6 @@ config GENERIC_ISA_DMA
bool
default y
-config HAVE_DEC_LOCK
- bool
- default y
-
config EARLY_PRINTK
bool
default y
Index: linux-2.6/arch/sparc64/lib/Makefile
===================================================================
--- linux-2.6.orig/arch/sparc64/lib/Makefile
+++ linux-2.6/arch/sparc64/lib/Makefile
@@ -14,6 +14,4 @@ lib-y := PeeCeeI.o copy_page.o clear_pag
copy_in_user.o user_fixup.o memmove.o \
mcount.o ipcsum.o rwsem.o xor.o find_bit.o delay.o
-lib-$(CONFIG_HAVE_DEC_LOCK) += dec_and_lock.o
-
obj-y += iomap.o
Index: linux-2.6/arch/x86_64/Kconfig
===================================================================
--- linux-2.6.orig/arch/x86_64/Kconfig
+++ linux-2.6/arch/x86_64/Kconfig
@@ -277,11 +277,6 @@ source "mm/Kconfig"
config HAVE_ARCH_EARLY_PFN_TO_NID
def_bool y
-config HAVE_DEC_LOCK
- bool
- depends on SMP
- default y
-
config NR_CPUS
int "Maximum number of CPUs (2-256)"
range 2 256
Index: linux-2.6/arch/x86_64/lib/Makefile
===================================================================
--- linux-2.6.orig/arch/x86_64/lib/Makefile
+++ linux-2.6/arch/x86_64/lib/Makefile
@@ -10,5 +10,3 @@ lib-y := csum-partial.o csum-copy.o csum
usercopy.o getuser.o putuser.o \
thunk.o clear_page.o copy_page.o bitstr.o bitops.o
lib-y += memcpy.o memmove.o memset.o copy_user.o
-
-lib-$(CONFIG_HAVE_DEC_LOCK) += dec_and_lock.o
Index: linux-2.6/arch/xtensa/Kconfig
===================================================================
--- linux-2.6.orig/arch/xtensa/Kconfig
+++ linux-2.6/arch/xtensa/Kconfig
@@ -26,10 +26,6 @@ config RWSEM_XCHGADD_ALGORITHM
bool
default y
-config HAVE_DEC_LOCK
- bool
- default y
-
config GENERIC_HARDIRQS
bool
default y
Index: linux-2.6/arch/sparc64/lib/dec_and_lock.S
===================================================================
--- linux-2.6.orig/arch/sparc64/lib/dec_and_lock.S
+++ /dev/null
@@ -1,80 +0,0 @@
-/* $Id: dec_and_lock.S,v 1.5 2001/11/18 00:12:56 davem Exp $
- * dec_and_lock.S: Sparc64 version of "atomic_dec_and_lock()"
- * using cas and ldstub instructions.
- *
- * Copyright (C) 2000 David S. Miller (davem@xxxxxxxxxx)
- */
-#include <linux/config.h>
-#include <asm/thread_info.h>
-
- .text
- .align 64
-
- /* CAS basically works like this:
- *
- * void CAS(MEM, REG1, REG2)
- * {
- * START_ATOMIC();
- * if (*(MEM) == REG1) {
- * TMP = *(MEM);
- * *(MEM) = REG2;
- * REG2 = TMP;
- * } else
- * REG2 = *(MEM);
- * END_ATOMIC();
- * }
- */
-
- .globl _atomic_dec_and_lock
-_atomic_dec_and_lock: /* %o0 = counter, %o1 = lock */
-loop1: lduw [%o0], %g2
- subcc %g2, 1, %g7
- be,pn %icc, start_to_zero
- nop
-nzero: cas [%o0], %g2, %g7
- cmp %g2, %g7
- bne,pn %icc, loop1
- mov 0, %g1
-
-out:
- membar #StoreLoad | #StoreStore
- retl
- mov %g1, %o0
-start_to_zero:
-#ifdef CONFIG_PREEMPT
- ldsw [%g6 + TI_PRE_COUNT], %g3
- add %g3, 1, %g3
- stw %g3, [%g6 + TI_PRE_COUNT]
-#endif
-to_zero:
- ldstub [%o1], %g3
- membar #StoreLoad | #StoreStore
- brnz,pn %g3, spin_on_lock
- nop
-loop2: cas [%o0], %g2, %g7 /* ASSERT(g7 == 0) */
- cmp %g2, %g7
-
- be,pt %icc, out
- mov 1, %g1
- lduw [%o0], %g2
- subcc %g2, 1, %g7
- be,pn %icc, loop2
- nop
- membar #StoreStore | #LoadStore
- stb %g0, [%o1]
-#ifdef CONFIG_PREEMPT
- ldsw [%g6 + TI_PRE_COUNT], %g3
- sub %g3, 1, %g3
- stw %g3, [%g6 + TI_PRE_COUNT]
-#endif
-
- b,pt %xcc, nzero
- nop
-spin_on_lock:
- ldub [%o1], %g3
- membar #LoadLoad
- brnz,pt %g3, spin_on_lock
- nop
- ba,pt %xcc, to_zero
- nop
- nop
Index: linux-2.6/arch/alpha/kernel/alpha_ksyms.c
===================================================================
--- linux-2.6.orig/arch/alpha/kernel/alpha_ksyms.c
+++ linux-2.6/arch/alpha/kernel/alpha_ksyms.c
@@ -184,7 +184,6 @@ EXPORT_SYMBOL(cpu_data);
EXPORT_SYMBOL(smp_num_cpus);
EXPORT_SYMBOL(smp_call_function);
EXPORT_SYMBOL(smp_call_function_on_cpu);
-EXPORT_SYMBOL(_atomic_dec_and_lock);
EXPORT_SYMBOL(cpu_present_mask);
#endif /* CONFIG_SMP */
Index: linux-2.6/arch/sparc64/kernel/sparc64_ksyms.c
===================================================================
--- linux-2.6.orig/arch/sparc64/kernel/sparc64_ksyms.c
+++ linux-2.6/arch/sparc64/kernel/sparc64_ksyms.c
@@ -163,9 +163,6 @@ EXPORT_SYMBOL(atomic64_add);
EXPORT_SYMBOL(atomic64_add_ret);
EXPORT_SYMBOL(atomic64_sub);
EXPORT_SYMBOL(atomic64_sub_ret);
-#ifdef CONFIG_SMP
-EXPORT_SYMBOL(_atomic_dec_and_lock);
-#endif
/* Atomic bit operations. */
EXPORT_SYMBOL(test_and_set_bit);
Index: linux-2.6/arch/x86_64/kernel/x8664_ksyms.c
===================================================================
--- linux-2.6.orig/arch/x86_64/kernel/x8664_ksyms.c
+++ linux-2.6/arch/x86_64/kernel/x8664_ksyms.c
@@ -178,10 +178,6 @@ EXPORT_SYMBOL(rwsem_down_write_failed_th
EXPORT_SYMBOL(empty_zero_page);
-#ifdef CONFIG_HAVE_DEC_LOCK
-EXPORT_SYMBOL(_atomic_dec_and_lock);
-#endif
-
EXPORT_SYMBOL(die_chain);
EXPORT_SYMBOL(register_die_notifier);
Index: linux-2.6/arch/alpha/lib/Makefile
===================================================================
--- linux-2.6.orig/arch/alpha/lib/Makefile
+++ linux-2.6/arch/alpha/lib/Makefile
@@ -40,8 +40,6 @@ lib-y = __divqu.o __remqu.o __divlu.o __
fpreg.o \
callback_srm.o srm_puts.o srm_printk.o
-lib-$(CONFIG_SMP) += dec_and_lock.o
-
# The division routines are built from single source, with different defines.
AFLAGS___divqu.o = -DDIV
AFLAGS___remqu.o = -DREM
Index: linux-2.6/arch/mips/lib/Makefile
===================================================================
--- linux-2.6.orig/arch/mips/lib/Makefile
+++ linux-2.6/arch/mips/lib/Makefile
@@ -2,8 +2,7 @@
# Makefile for MIPS-specific library files..
#
-lib-y += csum_partial_copy.o dec_and_lock.o memcpy.o promlib.o \
- strlen_user.o strncpy_user.o strnlen_user.o
+lib-y += csum_partial_copy.o memcpy.o promlib.o strlen_user.o strncpy_user.o strnlen_user.o
obj-y += iomap.o
Index: linux-2.6/arch/ppc/lib/Makefile
===================================================================
--- linux-2.6.orig/arch/ppc/lib/Makefile
+++ linux-2.6/arch/ppc/lib/Makefile
@@ -2,7 +2,7 @@
# Makefile for ppc-specific library files..
#
-obj-y := checksum.o string.o strcase.o dec_and_lock.o div64.o
+obj-y := checksum.o string.o strcase.o div64.o
obj-$(CONFIG_8xx) += rheap.o
obj-$(CONFIG_CPM2) += rheap.o
Index: linux-2.6/arch/ppc64/lib/Makefile
===================================================================
--- linux-2.6.orig/arch/ppc64/lib/Makefile
+++ linux-2.6/arch/ppc64/lib/Makefile
@@ -2,7 +2,7 @@
# Makefile for ppc64-specific library files..
#
-lib-y := checksum.o dec_and_lock.o string.o strcase.o
+lib-y := checksum.o string.o strcase.o
lib-y += copypage.o memcpy.o copyuser.o usercopy.o
# Lock primitives are defined as no-ops in include/linux/spinlock.h
Index: linux-2.6/arch/sparc64/Kconfig.debug
===================================================================
--- linux-2.6.orig/arch/sparc64/Kconfig.debug
+++ linux-2.6/arch/sparc64/Kconfig.debug
@@ -33,14 +33,6 @@ config DEBUG_BOOTMEM
depends on DEBUG_KERNEL
bool "Debug BOOTMEM initialization"
-# We have a custom atomic_dec_and_lock() implementation but it's not
-# compatible with spinlock debugging so we need to fall back on
-# the generic version in that case.
-config HAVE_DEC_LOCK
- bool
- depends on SMP && !DEBUG_SPINLOCK
- default y
-
config MCOUNT
bool
depends on STACK_DEBUG
Index: linux-2.6/kernel/rcupdate.c
===================================================================
--- linux-2.6.orig/kernel/rcupdate.c
+++ linux-2.6/kernel/rcupdate.c
@@ -45,7 +45,6 @@
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/rcupdate.h>
-#include <linux/rcuref.h>
#include <linux/cpu.h>
/* Definition for rcupdate control block. */
@@ -73,19 +72,6 @@ DEFINE_PER_CPU(struct rcu_data, rcu_bh_d
static DEFINE_PER_CPU(struct tasklet_struct, rcu_tasklet) = {NULL};
static int maxbatch = 10;
-#ifndef __HAVE_ARCH_CMPXCHG
-/*
- * We use an array of spinlocks for the rcurefs -- similar to ones in sparc
- * 32 bit atomic_t implementations, and a hash function similar to that
- * for our refcounting needs.
- * Can't help multiprocessors which donot have cmpxchg :(
- */
-
-spinlock_t __rcuref_hash[RCUREF_HASH_SIZE] = {
- [0 ... (RCUREF_HASH_SIZE-1)] = SPIN_LOCK_UNLOCKED
-};
-#endif
-
/**
* call_rcu - Queue an RCU callback for invocation after a grace period.
* @head: structure to be used for queueing the RCU updates.