I was about to, like several other platforms, copy over the
cmpxchg() _atomic_dec_and_lock() implementation from ppc64,
but then I looked around and noticed how rediculious all of
this duplication is.
So how about we do the following. If the platform has cmpxchg()
then we use the ppc64 C version, else we use the existing code
in lib/dec_and_lock.c
Here is my analysis of the existing implementations:
1) Alpha - is trying to define a fast path for the case where
we don't decrement to zero, presumably to avoid setting up
a full stack frame in that case.
The memory operations are so much more expensive than whatever
cycles are being saved here, that considering that and the
maintainability gains we're getting by this change it is
an acceptable result.
2) i386/x86_64 - similar to ppc64 C code which is now used except
that cmpxchg() macro was open coded. The new generic version
should end up producing similar if not identical code.
3) ia64 - almost identical to ppc64 C code version, except the
looping is done slightly differently. I see no functional
difference resulting from the new code.
4) mips - used a copy of the ppc64 C code, so no issues
5) ppc - used a copy of the ppc64 C code, so no issues
6) sparc64 - too ugly for words, in hand coded assembler and
probably buggy, it's what led me to work on this patch
I really think this is the way to go.
Comments?
diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
--- a/arch/alpha/Kconfig
+++ b/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
diff --git a/arch/alpha/kernel/alpha_ksyms.c b/arch/alpha/kernel/alpha_ksyms.c
--- a/arch/alpha/kernel/alpha_ksyms.c
+++ b/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 */
diff --git a/arch/alpha/lib/Makefile b/arch/alpha/lib/Makefile
--- a/arch/alpha/lib/Makefile
+++ b/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
diff --git a/arch/alpha/lib/dec_and_lock.c b/arch/alpha/lib/dec_and_lock.c
deleted file mode 100644
--- a/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 $atomic_dec_and_lock_1..ng \n\
- .subsection 2 \n\
-4: br 1b \n\
- .previous \n\
- .end _atomic_dec_and_lock");
-
-static int __attribute_used__
-atomic_dec_and_lock_1(atomic_t *atomic, spinlock_t *lock)
-{
- /* Slow path */
- spin_lock(lock);
- if (atomic_dec_and_test(atomic))
- return 1;
- spin_unlock(lock);
- return 0;
-}
diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig
--- a/arch/i386/Kconfig
+++ b/arch/i386/Kconfig
@@ -908,11 +908,6 @@ config IRQBALANCE
The default yes will allow the kernel to do irq load balancing.
Saying no will keep the kernel from doing irq load balancing.
-config HAVE_DEC_LOCK
- bool
- depends on (SMP || PREEMPT) && X86_CMPXCHG
- default y
-
# turning this on wastes a bunch of space.
# Summit needs it only when NUMA is on
config BOOT_IOREMAP
diff --git a/arch/i386/lib/Makefile b/arch/i386/lib/Makefile
--- a/arch/i386/lib/Makefile
+++ b/arch/i386/lib/Makefile
@@ -7,4 +7,3 @@ lib-y = checksum.o delay.o usercopy.o ge
bitops.o
lib-$(CONFIG_X86_USE_3DNOW) += mmx.o
-lib-$(CONFIG_HAVE_DEC_LOCK) += dec_and_lock.o
diff --git a/arch/i386/lib/dec_and_lock.c b/arch/i386/lib/dec_and_lock.c
deleted file mode 100644
--- a/arch/i386/lib/dec_and_lock.c
+++ /dev/null
@@ -1,42 +0,0 @@
-/*
- * x86 version of "atomic_dec_and_lock()" using
- * the atomic "cmpxchg" instruction.
- *
- * (For CPU's lacking cmpxchg, we use the slow
- * generic version, and this one never even gets
- * compiled).
- */
-
-#include <linux/spinlock.h>
-#include <linux/module.h>
-#include <asm/atomic.h>
-
-int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
-{
- int counter;
- int newcount;
-
-repeat:
- counter = atomic_read(atomic);
- newcount = counter-1;
-
- if (!newcount)
- goto slow_path;
-
- asm volatile("lock; cmpxchgl %1,%2"
- :"=a" (newcount)
- :"r" (newcount), "m" (atomic->counter), "0" (counter));
-
- /* If the above failed, "eax" will have changed */
- if (newcount != counter)
- goto repeat;
- return 0;
-
-slow_path:
- spin_lock(lock);
- if (atomic_dec_and_test(atomic))
- return 1;
- spin_unlock(lock);
- return 0;
-}
-EXPORT_SYMBOL(_atomic_dec_and_lock);
diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -298,11 +298,6 @@ config PREEMPT
source "mm/Kconfig"
-config HAVE_DEC_LOCK
- bool
- depends on (SMP || PREEMPT)
- default y
-
config IA32_SUPPORT
bool "Support for Linux/x86 binaries"
help
diff --git a/arch/ia64/lib/Makefile b/arch/ia64/lib/Makefile
--- a/arch/ia64/lib/Makefile
+++ b/arch/ia64/lib/Makefile
@@ -15,7 +15,6 @@ lib-$(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
diff --git a/arch/ia64/lib/dec_and_lock.c b/arch/ia64/lib/dec_and_lock.c
deleted file mode 100644
--- a/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 <[EMAIL PROTECTED]>
- *
- * 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);
diff --git a/arch/m32r/Kconfig b/arch/m32r/Kconfig
--- a/arch/m32r/Kconfig
+++ b/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---
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
--- a/arch/mips/Kconfig
+++ b/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.
#
diff --git a/arch/mips/lib/Makefile b/arch/mips/lib/Makefile
--- a/arch/mips/lib/Makefile
+++ b/arch/mips/lib/Makefile
@@ -2,7 +2,7 @@
# Makefile for MIPS-specific library files..
#
-lib-y += csum_partial_copy.o dec_and_lock.o memcpy.o promlib.o \
+lib-y += csum_partial_copy.o memcpy.o promlib.o \
strlen_user.o strncpy_user.o strnlen_user.o
obj-y += iomap.o
diff --git a/arch/mips/lib/dec_and_lock.c b/arch/mips/lib/dec_and_lock.c
deleted file mode 100644
--- a/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);
diff --git a/arch/ppc/Kconfig b/arch/ppc/Kconfig
--- a/arch/ppc/Kconfig
+++ b/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
diff --git a/arch/ppc/lib/Makefile b/arch/ppc/lib/Makefile
--- a/arch/ppc/lib/Makefile
+++ b/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
diff --git a/arch/ppc/lib/dec_and_lock.c b/arch/ppc/lib/dec_and_lock.c
deleted file mode 100644
--- a/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);
diff --git a/arch/ppc64/Kconfig b/arch/ppc64/Kconfig
--- a/arch/ppc64/Kconfig
+++ b/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
diff --git a/arch/ppc64/lib/Makefile b/arch/ppc64/lib/Makefile
--- a/arch/ppc64/lib/Makefile
+++ b/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
diff --git a/arch/ppc64/lib/dec_and_lock.c b/arch/ppc64/lib/dec_and_lock.c
deleted file mode 100644
--- a/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);
diff --git a/arch/sparc64/Kconfig.debug b/arch/sparc64/Kconfig.debug
--- a/arch/sparc64/Kconfig.debug
+++ b/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
diff --git a/arch/sparc64/kernel/sparc64_ksyms.c
b/arch/sparc64/kernel/sparc64_ksyms.c
--- a/arch/sparc64/kernel/sparc64_ksyms.c
+++ b/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);
diff --git a/arch/sparc64/lib/Makefile b/arch/sparc64/lib/Makefile
--- a/arch/sparc64/lib/Makefile
+++ b/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
diff --git a/arch/sparc64/lib/dec_and_lock.S b/arch/sparc64/lib/dec_and_lock.S
deleted file mode 100644
--- a/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 ([email protected])
- */
-#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
diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
--- a/arch/x86_64/Kconfig
+++ b/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
diff --git a/arch/x86_64/kernel/x8664_ksyms.c b/arch/x86_64/kernel/x8664_ksyms.c
--- a/arch/x86_64/kernel/x8664_ksyms.c
+++ b/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);
diff --git a/arch/x86_64/lib/Makefile b/arch/x86_64/lib/Makefile
--- a/arch/x86_64/lib/Makefile
+++ b/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-$(CONFIG_HAVE_DEC_LOCK) += dec_and_lock.o
diff --git a/arch/x86_64/lib/dec_and_lock.c b/arch/x86_64/lib/dec_and_lock.c
deleted file mode 100644
--- a/arch/x86_64/lib/dec_and_lock.c
+++ /dev/null
@@ -1,40 +0,0 @@
-/*
- * x86 version of "atomic_dec_and_lock()" using
- * the atomic "cmpxchg" instruction.
- *
- * (For CPU's lacking cmpxchg, we use the slow
- * generic version, and this one never even gets
- * compiled).
- */
-
-#include <linux/spinlock.h>
-#include <asm/atomic.h>
-
-int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
-{
- int counter;
- int newcount;
-
-repeat:
- counter = atomic_read(atomic);
- newcount = counter-1;
-
- if (!newcount)
- goto slow_path;
-
- asm volatile("lock; cmpxchgl %1,%2"
- :"=a" (newcount)
- :"r" (newcount), "m" (atomic->counter), "0" (counter));
-
- /* If the above failed, "eax" will have changed */
- if (newcount != counter)
- goto repeat;
- return 0;
-
-slow_path:
- spin_lock(lock);
- if (atomic_dec_and_test(atomic))
- return 1;
- spin_unlock(lock);
- return 0;
-}
diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -26,10 +26,6 @@ config RWSEM_XCHGADD_ALGORITHM
bool
default y
-config HAVE_DEC_LOCK
- bool
- default y
-
config GENERIC_HARDIRQS
bool
default y
diff --git a/lib/Makefile b/lib/Makefile
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -5,7 +5,7 @@
lib-y := errno.o ctype.o string.o vsprintf.o cmdline.o \
bust_spinlocks.o rbtree.o radix-tree.o dump_stack.o \
idr.o div64.o int_sqrt.o bitmap.o extable.o prio_tree.o \
- sha1.o
+ sha1.o dec_and_lock.o
lib-y += kobject.o kref.o kobject_uevent.o klist.o
@@ -24,10 +24,6 @@ lib-$(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
diff --git a/lib/dec_and_lock.c b/lib/dec_and_lock.c
--- a/lib/dec_and_lock.c
+++ b/lib/dec_and_lock.c
@@ -1,7 +1,41 @@
#include <linux/module.h>
#include <linux/spinlock.h>
#include <asm/atomic.h>
+#include <asm/system.h>
+#ifdef __HAVE_ARCH_CMPXCHG
+/*
+ * 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;
+}
+#else
/*
* This is an architecture-neutral, but slow,
* implementation of the notion of "decrement
@@ -33,5 +67,6 @@ int _atomic_dec_and_lock(atomic_t *atomi
spin_unlock(lock);
return 0;
}
+#endif
EXPORT_SYMBOL(_atomic_dec_and_lock);
