e79bee24fd
The x86 implementation of atomic_dec_if_positive is quite generic, so make it available to all architectures. This is needed for "swap: add a simple detector for inappropriate swapin readahead". [akpm@linux-foundation.org: do the "#define foo foo" trick in the conventional manner] Signed-off-by: Shaohua Li <shli@fusionio.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: "David S. Miller" <davem@davemloft.net> Cc: Rik van Riel <riel@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Michal Simek <monstr@monstr.eu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
132 lines
3 KiB
C
132 lines
3 KiB
C
/* Atomic operations usable in machine independent code */
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#ifndef _LINUX_ATOMIC_H
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#define _LINUX_ATOMIC_H
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#include <asm/atomic.h>
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/**
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* atomic_add_unless - add unless the number is already a given value
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* @v: pointer of type atomic_t
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* @a: the amount to add to v...
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* @u: ...unless v is equal to u.
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*
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* Atomically adds @a to @v, so long as @v was not already @u.
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* Returns non-zero if @v was not @u, and zero otherwise.
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*/
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static inline int atomic_add_unless(atomic_t *v, int a, int u)
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{
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return __atomic_add_unless(v, a, u) != u;
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}
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/**
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* atomic_inc_not_zero - increment unless the number is zero
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* @v: pointer of type atomic_t
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*
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* Atomically increments @v by 1, so long as @v is non-zero.
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* Returns non-zero if @v was non-zero, and zero otherwise.
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*/
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#ifndef atomic_inc_not_zero
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#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
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#endif
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/**
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* atomic_inc_not_zero_hint - increment if not null
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* @v: pointer of type atomic_t
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* @hint: probable value of the atomic before the increment
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*
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* This version of atomic_inc_not_zero() gives a hint of probable
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* value of the atomic. This helps processor to not read the memory
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* before doing the atomic read/modify/write cycle, lowering
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* number of bus transactions on some arches.
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*
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* Returns: 0 if increment was not done, 1 otherwise.
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*/
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#ifndef atomic_inc_not_zero_hint
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static inline int atomic_inc_not_zero_hint(atomic_t *v, int hint)
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{
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int val, c = hint;
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/* sanity test, should be removed by compiler if hint is a constant */
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if (!hint)
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return atomic_inc_not_zero(v);
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do {
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val = atomic_cmpxchg(v, c, c + 1);
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if (val == c)
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return 1;
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c = val;
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} while (c);
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return 0;
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}
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#endif
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#ifndef atomic_inc_unless_negative
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static inline int atomic_inc_unless_negative(atomic_t *p)
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{
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int v, v1;
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for (v = 0; v >= 0; v = v1) {
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v1 = atomic_cmpxchg(p, v, v + 1);
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if (likely(v1 == v))
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return 1;
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}
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return 0;
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}
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#endif
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#ifndef atomic_dec_unless_positive
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static inline int atomic_dec_unless_positive(atomic_t *p)
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{
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int v, v1;
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for (v = 0; v <= 0; v = v1) {
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v1 = atomic_cmpxchg(p, v, v - 1);
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if (likely(v1 == v))
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return 1;
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}
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return 0;
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}
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#endif
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/*
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* atomic_dec_if_positive - decrement by 1 if old value positive
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* @v: pointer of type atomic_t
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*
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* The function returns the old value of *v minus 1, even if
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* the atomic variable, v, was not decremented.
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*/
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#ifndef atomic_dec_if_positive
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static inline int atomic_dec_if_positive(atomic_t *v)
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{
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int c, old, dec;
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c = atomic_read(v);
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for (;;) {
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dec = c - 1;
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if (unlikely(dec < 0))
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break;
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old = atomic_cmpxchg((v), c, dec);
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if (likely(old == c))
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break;
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c = old;
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}
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return dec;
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}
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#endif
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#ifndef CONFIG_ARCH_HAS_ATOMIC_OR
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static inline void atomic_or(int i, atomic_t *v)
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{
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int old;
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int new;
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do {
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old = atomic_read(v);
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new = old | i;
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} while (atomic_cmpxchg(v, old, new) != old);
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}
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#endif /* #ifndef CONFIG_ARCH_HAS_ATOMIC_OR */
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#include <asm-generic/atomic-long.h>
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#ifdef CONFIG_GENERIC_ATOMIC64
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#include <asm-generic/atomic64.h>
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#endif
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#endif /* _LINUX_ATOMIC_H */
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