diff options
author | David S. Miller <davem@davemloft.net> | 2005-09-14 21:47:01 -0700 |
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committer | David S. Miller <davem@davemloft.net> | 2005-09-14 21:47:01 -0700 |
commit | 4db2ce0199f04b6e99999f22e28ef9a0ae5f0d2f (patch) | |
tree | 87a00c97e02a77cdfec517398caa3f1d8f6a2f0d | |
parent | 4a805e863d6b9466baf7084e1d6fdbe6e0628d8e (diff) | |
download | linux-4db2ce0199f04b6e99999f22e28ef9a0ae5f0d2f.tar.gz linux-4db2ce0199f04b6e99999f22e28ef9a0ae5f0d2f.tar.bz2 linux-4db2ce0199f04b6e99999f22e28ef9a0ae5f0d2f.zip |
[LIB]: Consolidate _atomic_dec_and_lock()
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>
-rw-r--r-- | arch/i386/Kconfig | 5 | ||||
-rw-r--r-- | arch/i386/lib/Makefile | 1 | ||||
-rw-r--r-- | arch/i386/lib/dec_and_lock.c | 42 | ||||
-rw-r--r-- | arch/ia64/Kconfig | 5 | ||||
-rw-r--r-- | arch/ia64/lib/Makefile | 1 | ||||
-rw-r--r-- | arch/ia64/lib/dec_and_lock.c | 42 | ||||
-rw-r--r-- | arch/m32r/Kconfig | 5 | ||||
-rw-r--r-- | arch/mips/Kconfig | 4 | ||||
-rw-r--r-- | arch/mips/lib/Makefile | 2 | ||||
-rw-r--r-- | arch/mips/lib/dec_and_lock.c | 47 | ||||
-rw-r--r-- | arch/ppc/Kconfig | 4 | ||||
-rw-r--r-- | arch/ppc/lib/Makefile | 2 | ||||
-rw-r--r-- | arch/ppc/lib/dec_and_lock.c | 38 | ||||
-rw-r--r-- | arch/ppc64/Kconfig | 4 | ||||
-rw-r--r-- | arch/ppc64/lib/Makefile | 2 | ||||
-rw-r--r-- | arch/ppc64/lib/dec_and_lock.c | 47 | ||||
-rw-r--r-- | arch/sparc64/Kconfig.debug | 8 | ||||
-rw-r--r-- | arch/sparc64/kernel/sparc64_ksyms.c | 3 | ||||
-rw-r--r-- | arch/sparc64/lib/Makefile | 2 | ||||
-rw-r--r-- | arch/sparc64/lib/dec_and_lock.S | 80 | ||||
-rw-r--r-- | arch/x86_64/Kconfig | 5 | ||||
-rw-r--r-- | arch/x86_64/kernel/x8664_ksyms.c | 4 | ||||
-rw-r--r-- | arch/x86_64/lib/Makefile | 2 | ||||
-rw-r--r-- | arch/x86_64/lib/dec_and_lock.c | 40 | ||||
-rw-r--r-- | arch/xtensa/Kconfig | 4 | ||||
-rw-r--r-- | lib/dec_and_lock.c | 35 |
26 files changed, 38 insertions, 396 deletions
diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig index b22f003eaa6d..d2703cda61ea 100644 --- 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 index 7b1932d20f96..914933e9ec3d 100644 --- a/arch/i386/lib/Makefile +++ b/arch/i386/lib/Makefile @@ -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 diff --git a/arch/i386/lib/dec_and_lock.c b/arch/i386/lib/dec_and_lock.c deleted file mode 100644 index 8b81b2524fa6..000000000000 --- 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 index ed25d66c8d50..945c15a0722b 100644 --- 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 index 799407e7726f..cb1af597370b 100644 --- a/arch/ia64/lib/Makefile +++ b/arch/ia64/lib/Makefile @@ -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 diff --git a/arch/ia64/lib/dec_and_lock.c b/arch/ia64/lib/dec_and_lock.c deleted file mode 100644 index c7ce92f968f1..000000000000 --- 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 <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); diff --git a/arch/m32r/Kconfig b/arch/m32r/Kconfig index 1ef3987ebc6a..4d100f3886e1 100644 --- 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 index 0eb71ac303af..4cd724c05700 100644 --- 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 index 21b92b9dd013..037303412909 100644 --- 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 index fd82c84a93b7..000000000000 --- 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 index 347ea284140b..776941c75672 100644 --- 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 index f1e1fb4144f0..50358e4ea159 100644 --- 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 index b18f0d9a00fc..000000000000 --- 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 index deca68ad644a..c658650af429 100644 --- 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 index 76fbfa9f706f..0b6e967de948 100644 --- 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 index 7b9d4da5cf92..000000000000 --- 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 index cd8d39fb954d..af0e9411b83e 100644 --- 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 index cbb5e59824e5..fb7a5370dbfc 100644 --- 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 index d968aebe83b2..c295806500f7 100644 --- a/arch/sparc64/lib/Makefile +++ b/arch/sparc64/lib/Makefile @@ -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 diff --git a/arch/sparc64/lib/dec_and_lock.S b/arch/sparc64/lib/dec_and_lock.S deleted file mode 100644 index 8ee288dd0afc..000000000000 --- 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 (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 diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig index e63323e03ea9..0969d570f3b5 100644 --- 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 index 68ec03070e5a..fd99ddd009bc 100644 --- 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_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); diff --git a/arch/x86_64/lib/Makefile b/arch/x86_64/lib/Makefile index 6b26a1c1e9ff..bba5db6cebd6 100644 --- 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-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 diff --git a/arch/x86_64/lib/dec_and_lock.c b/arch/x86_64/lib/dec_and_lock.c deleted file mode 100644 index ab43394dc775..000000000000 --- 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 index 2b6257bec4c3..7e841aa2a4aa 100644 --- 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/dec_and_lock.c b/lib/dec_and_lock.c index 2377af057d09..305a9663aee3 100644 --- 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 *atomic, spinlock_t *lock) spin_unlock(lock); return 0; } +#endif EXPORT_SYMBOL(_atomic_dec_and_lock); |