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
|
|
#define _ASM_GENERIC_LOCAL_H
|
|
|
|
#include <linux/config.h>
|
|
#include <linux/percpu.h>
|
|
#include <linux/hardirq.h>
|
|
#include <asm/atomic.h>
|
|
#include <asm/types.h>
|
|
|
|
/* An unsigned long type for operations which are atomic for a single
|
|
* CPU. Usually used in combination with per-cpu variables. */
|
|
|
|
/* Implement in terms of atomics. */
|
|
|
|
/* Don't use typedef: don't want them to be mixed with atomic_t's. */
|
|
typedef struct
|
|
{
|
|
atomic_long_t a;
|
|
} local_t;
|
|
|
|
#define LOCAL_INIT(i) { ATOMIC_LONG_INIT(i) }
|
|
|
|
#define local_read(l) ((unsigned long)atomic_long_read(&(l)->a))
|
|
#define local_set(l,i) atomic_long_set((&(l)->a),(i))
|
|
#define local_inc(l) atomic_long_inc(&(l)->a)
|
|
#define local_dec(l) atomic_long_dec(&(l)->a)
|
|
#define local_add(i,l) atomic_long_add((i),(&(l)->a))
|
|
#define local_sub(i,l) atomic_long_sub((i),(&(l)->a))
|
|
|
|
/* Non-atomic variants, ie. preemption disabled and won't be touched
|
|
* in interrupt, etc. Some archs can optimize this case well. */
|
|
#define __local_inc(l) local_set((l), local_read(l) + 1)
|
|
#define __local_dec(l) local_set((l), local_read(l) - 1)
|
|
#define __local_add(i,l) local_set((l), local_read(l) + (i))
|
|
#define __local_sub(i,l) local_set((l), local_read(l) - (i))
|
|
|
|
/* Use these for per-cpu local_t variables: on some archs they are
|
|
* much more efficient than these naive implementations. Note they take
|
|
* a variable (eg. mystruct.foo), not an address.
|
|
*/
|
|
#define cpu_local_read(v) local_read(&__get_cpu_var(v))
|
|
#define cpu_local_set(v, i) local_set(&__get_cpu_var(v), (i))
|
|
#define cpu_local_inc(v) local_inc(&__get_cpu_var(v))
|
|
#define cpu_local_dec(v) local_dec(&__get_cpu_var(v))
|
|
#define cpu_local_add(i, v) local_add((i), &__get_cpu_var(v))
|
|
#define cpu_local_sub(i, v) local_sub((i), &__get_cpu_var(v))
|
|
|
|
/* Non-atomic increments, ie. preemption disabled and won't be touched
|
|
* in interrupt, etc. Some archs can optimize this case well.
|
|
*/
|
|
#define __cpu_local_inc(v) __local_inc(&__get_cpu_var(v))
|
|
#define __cpu_local_dec(v) __local_dec(&__get_cpu_var(v))
|
|
#define __cpu_local_add(i, v) __local_add((i), &__get_cpu_var(v))
|
|
#define __cpu_local_sub(i, v) __local_sub((i), &__get_cpu_var(v))
|
|
|
|
#endif /* _ASM_GENERIC_LOCAL_H */
|