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This series extena and standardises local_t operations on each architecture, allowing a rich set of atomic operations to be done on per-cpu data with minimal performance impact. On architectures where there seems to be no difference between the SMP and UP operation (same memory barriers, same LOCKing), local.h simply includes asm-generic/local.h, which removes duplicated code from the current kernel tree. This patch: local_t: architecture independent extension Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
76 lines
3.1 KiB
C
76 lines
3.1 KiB
C
#ifndef _ASM_GENERIC_LOCAL_H
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#define _ASM_GENERIC_LOCAL_H
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#include <linux/percpu.h>
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#include <linux/hardirq.h>
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#include <asm/atomic.h>
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#include <asm/types.h>
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/*
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* A signed long type for operations which are atomic for a single CPU.
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* Usually used in combination with per-cpu variables.
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*
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* This is the default implementation, which uses atomic_long_t. Which is
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* rather pointless. The whole point behind local_t is that some processors
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* can perform atomic adds and subtracts in a manner which is atomic wrt IRQs
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* running on this CPU. local_t allows exploitation of such capabilities.
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*/
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/* Implement in terms of atomics. */
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/* Don't use typedef: don't want them to be mixed with atomic_t's. */
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typedef struct
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{
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atomic_long_t a;
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} local_t;
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#define LOCAL_INIT(i) { ATOMIC_LONG_INIT(i) }
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#define local_read(l) atomic_long_read(&(l)->a)
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#define local_set(l,i) atomic_long_set((&(l)->a),(i))
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#define local_inc(l) atomic_long_inc(&(l)->a)
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#define local_dec(l) atomic_long_dec(&(l)->a)
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#define local_add(i,l) atomic_long_add((i),(&(l)->a))
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#define local_sub(i,l) atomic_long_sub((i),(&(l)->a))
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#define local_sub_and_test(i, l) atomic_long_sub_and_test((i), (&(l)->a))
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#define local_dec_and_test(l) atomic_long_dec_and_test(&(l)->a)
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#define local_inc_and_test(l) atomic_long_inc_and_test(&(l)->a)
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#define local_add_negative(i, l) atomic_long_add_negative((i), (&(l)->a))
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#define local_add_return(i, l) atomic_long_add_return((i), (&(l)->a))
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#define local_sub_return(i, l) atomic_long_sub_return((i), (&(l)->a))
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#define local_inc_return(l) atomic_long_inc_return(&(l)->a)
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#define local_cmpxchg(l, o, n) atomic_long_cmpxchg((&(l)->a), (o), (n))
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#define local_xchg(l, n) atomic_long_xchg((&(l)->a), (n))
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#define local_add_unless(l, a, u) atomic_long_add_unless((&(l)->a), (a), (u))
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#define local_inc_not_zero(l) atomic_long_inc_not_zero(&(l)->a)
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/* Non-atomic variants, ie. preemption disabled and won't be touched
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* in interrupt, etc. Some archs can optimize this case well. */
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#define __local_inc(l) local_set((l), local_read(l) + 1)
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#define __local_dec(l) local_set((l), local_read(l) - 1)
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#define __local_add(i,l) local_set((l), local_read(l) + (i))
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#define __local_sub(i,l) local_set((l), local_read(l) - (i))
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/* Use these for per-cpu local_t variables: on some archs they are
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* much more efficient than these naive implementations. Note they take
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* a variable (eg. mystruct.foo), not an address.
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*/
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#define cpu_local_read(l) local_read(&__get_cpu_var(l))
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#define cpu_local_set(l, i) local_set(&__get_cpu_var(l), (i))
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#define cpu_local_inc(l) local_inc(&__get_cpu_var(l))
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#define cpu_local_dec(l) local_dec(&__get_cpu_var(l))
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#define cpu_local_add(i, l) local_add((i), &__get_cpu_var(l))
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#define cpu_local_sub(i, l) local_sub((i), &__get_cpu_var(l))
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/* Non-atomic increments, ie. preemption disabled and won't be touched
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* in interrupt, etc. Some archs can optimize this case well.
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*/
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#define __cpu_local_inc(l) __local_inc(&__get_cpu_var(l))
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#define __cpu_local_dec(l) __local_dec(&__get_cpu_var(l))
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#define __cpu_local_add(i, l) __local_add((i), &__get_cpu_var(l))
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#define __cpu_local_sub(i, l) __local_sub((i), &__get_cpu_var(l))
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#endif /* _ASM_GENERIC_LOCAL_H */
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