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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 422 | giacomo | 1 | #ifndef __LINUX_PERCPU_H |
| 2 | #define __LINUX_PERCPU_H |
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| 3 | #include <linux/spinlock.h> /* For preempt_disable() */ |
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| 4 | #include <linux/slab.h> /* For kmalloc() */ |
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| 5 | #include <linux/smp.h> |
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| 6 | #include <linux/string.h> /* For memset() */ |
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| 7 | #include <asm/percpu.h> |
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| 8 | |||
| 9 | /* Enough to cover all DEFINE_PER_CPUs in kernel, including modules. */ |
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| 10 | #ifndef PERCPU_ENOUGH_ROOM |
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| 11 | #define PERCPU_ENOUGH_ROOM 32768 |
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| 12 | #endif |
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| 13 | |||
| 14 | /* Must be an lvalue. */ |
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| 15 | #define get_cpu_var(var) (*({ preempt_disable(); &__get_cpu_var(var); })) |
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| 16 | #define put_cpu_var(var) preempt_enable() |
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| 17 | |||
| 18 | #ifdef CONFIG_SMP |
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| 19 | |||
| 20 | struct percpu_data { |
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| 21 | void *ptrs[NR_CPUS]; |
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| 22 | void *blkp; |
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| 23 | }; |
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| 24 | |||
| 25 | /* |
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| 26 | * Use this to get to a cpu's version of the per-cpu object allocated using |
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| 27 | * alloc_percpu. If you want to get "this cpu's version", maybe you want |
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| 28 | * to use get_cpu_ptr... |
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| 29 | */ |
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| 30 | #define per_cpu_ptr(ptr, cpu) \ |
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| 31 | ({ \ |
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| 32 | struct percpu_data *__p = (struct percpu_data *)~(unsigned long)(ptr); \ |
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| 33 | (__typeof__(ptr))__p->ptrs[(cpu)]; \ |
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| 34 | }) |
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| 35 | |||
| 36 | extern void *__alloc_percpu(size_t size, size_t align); |
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| 37 | extern void free_percpu(const void *); |
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| 38 | extern void kmalloc_percpu_init(void); |
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| 39 | |||
| 40 | #else /* CONFIG_SMP */ |
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| 41 | |||
| 42 | #define per_cpu_ptr(ptr, cpu) (ptr) |
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| 43 | |||
| 44 | static inline void *__alloc_percpu(size_t size, size_t align) |
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| 45 | { |
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| 46 | void *ret = kmalloc(size, GFP_KERNEL); |
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| 47 | if (ret) |
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| 48 | memset(ret, 0, size); |
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| 49 | return ret; |
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| 50 | } |
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| 51 | static inline void free_percpu(const void *ptr) |
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| 52 | { |
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| 53 | kfree(ptr); |
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| 54 | } |
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| 55 | static inline void kmalloc_percpu_init(void) { } |
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| 56 | |||
| 57 | #endif /* CONFIG_SMP */ |
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| 58 | |||
| 59 | /* Simple wrapper for the common case: zeros memory. */ |
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| 60 | #define alloc_percpu(type) \ |
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| 61 | ((type *)(__alloc_percpu(sizeof(type), __alignof__(type)))) |
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| 62 | |||
| 63 | /* |
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| 64 | * Use these with alloc_percpu. If |
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| 65 | * 1. You want to operate on memory allocated by alloc_percpu (dereference |
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| 66 | * and read/modify/write) AND |
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| 67 | * 2. You want "this cpu's version" of the object AND |
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| 68 | * 3. You want to do this safely since: |
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| 69 | * a. On multiprocessors, you don't want to switch between cpus after |
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| 70 | * you've read the current processor id due to preemption -- this would |
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| 71 | * take away the implicit advantage to not have any kind of traditional |
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| 72 | * serialization for per-cpu data |
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| 73 | * b. On uniprocessors, you don't want another kernel thread messing |
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| 74 | * up with the same per-cpu data due to preemption |
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| 75 | * |
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| 76 | * So, Use get_cpu_ptr to disable preemption and get pointer to the |
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| 77 | * local cpu version of the per-cpu object. Use put_cpu_ptr to enable |
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| 78 | * preemption. Operations on per-cpu data between get_ and put_ is |
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| 79 | * then considered to be safe. And ofcourse, "Thou shalt not sleep between |
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| 80 | * get_cpu_ptr and put_cpu_ptr" |
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| 81 | */ |
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| 82 | #define get_cpu_ptr(ptr) per_cpu_ptr(ptr, get_cpu()) |
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| 83 | #define put_cpu_ptr(ptr) put_cpu() |
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| 84 | |||
| 85 | #endif /* __LINUX_PERCPU_H */ |