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[LIB]: Consolidate _atomic_dec_and_lock()

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Several implementations were essentialy a common piece of C code using
the cmpxchg() macro.  Put the implementation in one spot that everyone
can share, and convert sparc64 over to using this.

Alpha is the lone arch-specific implementation, which codes up a
special fast path for the common case in order to avoid GP reloading
which a pure C version would require.

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2005-09-14 21:47:01 -07:00
parent 4a805e863d
commit 4db2ce0199
26 changed files with 38 additions and 396 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

5
arch/i386/Kconfig
View file

@ -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

1
arch/i386/lib/Makefile
View file

@ -7,4 +7,3 @@ lib-y = checksum.o delay.o usercopy.o getuser.o putuser.o memcpy.o strstr.o \
bitops.o
lib-$(CONFIG_X86_USE_3DNOW) += mmx.o
lib-$(CONFIG_HAVE_DEC_LOCK) += dec_and_lock.o

42
arch/i386/lib/dec_and_lock.c
View file

@ -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);

5
arch/ia64/Kconfig
View file

@ -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

1
arch/ia64/lib/Makefile
View file

@ -15,7 +15,6 @@ lib-$(CONFIG_ITANIUM) += copy_page.o copy_user.o memcpy.o
lib-$(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

42
arch/ia64/lib/dec_and_lock.c
View file

@ -1,42 +0,0 @@
/*
* Copyright (C) 2003 Jerome Marchand, Bull S.A.
* Cleaned up by David Mosberger-Tang <davidm@hpl.hp.com>
*
* 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);

5
arch/m32r/Kconfig
View file

@ -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---

4
arch/mips/Kconfig
View file

@ -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.
#

2
arch/mips/lib/Makefile
View file

@ -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

47
arch/mips/lib/dec_and_lock.c
View file

@ -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);

4
arch/ppc/Kconfig
View file

@ -26,10 +26,6 @@ config GENERIC_CALIBRATE_DELAY
bool
default y
config HAVE_DEC_LOCK
bool
default y
config PPC
bool
default y

2
arch/ppc/lib/Makefile
View file

@ -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

38
arch/ppc/lib/dec_and_lock.c
View file

@ -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);

4
arch/ppc64/Kconfig
View file

@ -28,10 +28,6 @@ config GENERIC_ISA_DMA
bool
default y
config HAVE_DEC_LOCK
bool
default y
config EARLY_PRINTK
bool
default y

2
arch/ppc64/lib/Makefile
View file

@ -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

47
arch/ppc64/lib/dec_and_lock.c
View file

@ -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);

8
arch/sparc64/Kconfig.debug
View file

@ -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

3
arch/sparc64/kernel/sparc64_ksyms.c
View file

@ -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);

2
arch/sparc64/lib/Makefile
View file

@ -14,6 +14,4 @@ lib-y := PeeCeeI.o copy_page.o clear_page.o strlen.o strncmp.o \
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

80
arch/sparc64/lib/dec_and_lock.S
View file

@ -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@redhat.com)
*/
#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

5
arch/x86_64/Kconfig
View file

@ -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

4
arch/x86_64/kernel/x8664_ksyms.c
View file

@ -178,10 +178,6 @@ EXPORT_SYMBOL(rwsem_down_write_failed_thunk);
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);

2
arch/x86_64/lib/Makefile
View file

@ -10,5 +10,3 @@ lib-y := csum-partial.o csum-copy.o csum-wrappers.o delay.o \
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

40
arch/x86_64/lib/dec_and_lock.c
View file

@ -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;
}

4
arch/xtensa/Kconfig
View file

@ -26,10 +26,6 @@ config RWSEM_XCHGADD_ALGORITHM
bool
default y
config HAVE_DEC_LOCK
bool
default y
config GENERIC_HARDIRQS
bool
default y

35
lib/dec_and_lock.c
View file

@ -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 *atomic, spinlock_t *lock)
spin_unlock(lock);
return 0;
}
#endif
EXPORT_SYMBOL(_atomic_dec_and_lock);