Revision 528ba4ef855bd184b7d68e3fa596b420fb4fa86a authored by Linus Torvalds on 31 October 2006, 03:31:20 UTC, committed by Linus Torvalds on 31 October 2006, 03:31:20 UTC
* 'upstream' of git://ftp.linux-mips.org/pub/scm/upstream-linus: [MIPS] MIPS doesn't need compat_sys_getdents. [MIPS] JMR3927: Fixup another victim of the irq pt_regs cleanup. [MIPS] EMMA 2 / Markeins: struct resource takes physical addresses. [MIPS] EMMA 2 / Markeins: Convert to name struct resource initialization. [MIPS] EMMA 2 / Markeins: Formitting fixes split from actual address fixes. [MIPS] EMMA 2 / Markeins: Fix build wreckage due to genirq wreckage. [MIPS] Ocelot G: Fix build error and numerous warnings. [MIPS] Fix return value of TXX9 SPI interrupt handler [MIPS] Au1000: Fix warning about unused variable. [MIPS] Wire up getcpu(2) and epoll_wait(2) syscalls. [MIPS] Make SB1 cache flushes not to use on_each_cpu [MIPS] Fix warning about unused definition in c-sb1.c [MIPS] SMTC: Make 8 the default number of processors. [MIPS] Oprofile: Fix MIPSxx counter number detection. [MIPS] Au1xx0 code sets incorrect mips_hpt_frequency [MIPS] Oprofile: fix on non-VSMP / non-SMTC SMP configurations.
dec_and_lock.c
#include <linux/module.h>
#include <linux/spinlock.h>
#include <asm/atomic.h>
/*
* This is an implementation of the notion of "decrement a
* reference count, and return locked if it decremented to zero".
*
* NOTE NOTE NOTE! This is _not_ equivalent to
*
* if (atomic_dec_and_test(&atomic)) {
* spin_lock(&lock);
* return 1;
* }
* return 0;
*
* because the spin-lock and the decrement must be
* "atomic".
*/
int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
{
#ifdef CONFIG_SMP
/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
if (atomic_add_unless(atomic, -1, 1))
return 0;
#endif
/* Otherwise do it the slow way */
spin_lock(lock);
if (atomic_dec_and_test(atomic))
return 1;
spin_unlock(lock);
return 0;
}
EXPORT_SYMBOL(_atomic_dec_and_lock);
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