From: Kyle McMartin Date: Tue, 28 Mar 2006 09:56:11 +0000 (-0800) Subject: [PATCH] Decrapify asm-generic/local.h X-Git-Tag: v2.6.17-rc1~259 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=f5f5370da4b3128b7dfd944b4fcbb5c7b6887348;p=linux-2.6-omap-h63xx.git [PATCH] Decrapify asm-generic/local.h 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 Cc: Benjamin LaHaise Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/include/asm-generic/local.h b/include/asm-generic/local.h index 16fc00360f7..de4614840c2 100644 --- a/include/asm-generic/local.h +++ b/include/asm-generic/local.h @@ -4,28 +4,28 @@ #include #include #include +#include #include /* An unsigned long type for operations which are atomic for a single * CPU. Usually used in combination with per-cpu variables. */ -#if BITS_PER_LONG == 32 /* Implement in terms of atomics. */ /* Don't use typedef: don't want them to be mixed with atomic_t's. */ typedef struct { - atomic_t a; + atomic_long_t a; } local_t; -#define LOCAL_INIT(i) { ATOMIC_INIT(i) } +#define LOCAL_INIT(i) { ATOMIC_LONG_INIT(i) } -#define local_read(l) ((unsigned long)atomic_read(&(l)->a)) -#define local_set(l,i) atomic_set((&(l)->a),(i)) -#define local_inc(l) atomic_inc(&(l)->a) -#define local_dec(l) atomic_dec(&(l)->a) -#define local_add(i,l) atomic_add((i),(&(l)->a)) -#define local_sub(i,l) atomic_sub((i),(&(l)->a)) +#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. */ @@ -34,68 +34,6 @@ typedef struct #define __local_add(i,l) local_set((l), local_read(l) + (i)) #define __local_sub(i,l) local_set((l), local_read(l) - (i)) -#else /* ... can't use atomics. */ -/* Implement in terms of three variables. - Another option would be to use local_irq_save/restore. */ - -typedef struct -{ - /* 0 = in hardirq, 1 = in softirq, 2 = usermode. */ - unsigned long v[3]; -} local_t; - -#define _LOCAL_VAR(l) ((l)->v[!in_interrupt() + !in_irq()]) - -#define LOCAL_INIT(i) { { (i), 0, 0 } } - -static inline unsigned long local_read(local_t *l) -{ - return l->v[0] + l->v[1] + l->v[2]; -} - -static inline void local_set(local_t *l, unsigned long v) -{ - l->v[0] = v; - l->v[1] = l->v[2] = 0; -} - -static inline void local_inc(local_t *l) -{ - preempt_disable(); - _LOCAL_VAR(l)++; - preempt_enable(); -} - -static inline void local_dec(local_t *l) -{ - preempt_disable(); - _LOCAL_VAR(l)--; - preempt_enable(); -} - -static inline void local_add(unsigned long v, local_t *l) -{ - preempt_disable(); - _LOCAL_VAR(l) += v; - preempt_enable(); -} - -static inline void local_sub(unsigned long v, local_t *l) -{ - preempt_disable(); - _LOCAL_VAR(l) -= v; - preempt_enable(); -} - -/* 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) ((l)->v[0]++) -#define __local_dec(l) ((l)->v[0]--) -#define __local_add(i,l) ((l)->v[0] += (i)) -#define __local_sub(i,l) ((l)->v[0] -= (i)) - -#endif /* Non-atomic implementation */ - /* 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.