forked from luck/tmp_suning_uos_patched
f5f5370da4
Now that Christoph Lameter's atomic_long_t support is merged in mainline, might as well convert asm-generic/local.h to use it, so the same code can be used for both sizes of 32 and 64-bit unsigned longs. akpm sayeth: Q: Is there any particular reason why these routines weren't simply implemented with local_save/restore_flags, if they are only meant to guarantee atomicity to the local cpu? I'm sure on most platforms this would be more efficient than using an atomic... A: The whole _point_ of local_t is to avoid local_irq_disable(). It's designed to exploit the fact that many CPUs can do incs and decs in a way which is atomic wrt local interrupts, but not atomic wrt SMP. But this patch makes sense, because asm-generic/local.h is just a fallback implementation for architectures which either cannot perform these local-irq-atomic operations, or its maintainers haven't yet got around to implementing them. We need more work done on local_t in the 2.6.17 timeframe - they're defined as unsigned long, but some architectures implement them as signed long. Signed-off-by: Kyle McMartin <kyle@parisc-linux.org> Cc: Benjamin LaHaise <bcrl@kvack.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
57 lines
2.1 KiB
C
57 lines
2.1 KiB
C
#ifndef _ASM_GENERIC_LOCAL_H
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#define _ASM_GENERIC_LOCAL_H
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#include <linux/config.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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/* An unsigned long type for operations which are atomic for a single
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* CPU. Usually used in combination with per-cpu variables. */
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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) ((unsigned long)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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/* 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(v) local_read(&__get_cpu_var(v))
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#define cpu_local_set(v, i) local_set(&__get_cpu_var(v), (i))
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#define cpu_local_inc(v) local_inc(&__get_cpu_var(v))
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#define cpu_local_dec(v) local_dec(&__get_cpu_var(v))
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#define cpu_local_add(i, v) local_add((i), &__get_cpu_var(v))
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#define cpu_local_sub(i, v) local_sub((i), &__get_cpu_var(v))
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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(v) __local_inc(&__get_cpu_var(v))
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#define __cpu_local_dec(v) __local_dec(&__get_cpu_var(v))
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#define __cpu_local_add(i, v) __local_add((i), &__get_cpu_var(v))
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#define __cpu_local_sub(i, v) __local_sub((i), &__get_cpu_var(v))
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#endif /* _ASM_GENERIC_LOCAL_H */
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