include/linux/percpu.h

   1 #ifndef __LINUX_PERCPU_H
   2 #define __LINUX_PERCPU_H
   3 #include <linux/spinlock.h> /* For preempt_disable() */
   4 #include <linux/slab.h> /* For kmalloc() */
   5 #include <linux/smp.h>
   6 #include <linux/string.h> /* For memset() */
   7 #include <asm/percpu.h>
   8
   9 /* Enough to cover all DEFINE_PER_CPUs in kernel, including modules. */
  10 #ifndef PERCPU_ENOUGH_ROOM
  11 #define PERCPU_ENOUGH_ROOM 32768
  12 #endif
  13
  14 /*
  15  * Must be an lvalue. Since @var must be a simple identifier,
  16  * we force a syntax error here if it isn't.
  17  */
  18 #define get_cpu_var(var) (*({                           \
  19         extern int simple_indentifier_##var(void);      \
  20         preempt_disable();                              \
  21         &__get_cpu_var(var); }))
  22 #define put_cpu_var(var) preempt_enable()
  23
  24 #ifdef CONFIG_SMP
  25
  26 struct percpu_data {
  27         void *ptrs[NR_CPUS];
  28 };
  29
  30 /*
  31  * Use this to get to a cpu's version of the per-cpu object allocated using
  32  * alloc_percpu.  Non-atomic access to the current CPU's version should
  33  * probably be combined with get_cpu()/put_cpu().
  34  */
  35 #define per_cpu_ptr(ptr, cpu)                   \
  36 ({                                              \
  37         struct percpu_data *__p = (struct percpu_data *)~(unsigned long)(ptr); \
  38         (__typeof__(ptr))__p->ptrs[(cpu)];      \
  39 })
  40
  41 extern void *__alloc_percpu(size_t size);
  42 extern void free_percpu(const void *);
  43
  44 #else /* CONFIG_SMP */
  45
  46 #define per_cpu_ptr(ptr, cpu) ({ (void)(cpu); (ptr); })
  47
  48 static inline void *__alloc_percpu(size_t size)
  49 {
  50         void *ret = kmalloc(size, GFP_KERNEL);
  51         if (ret)
  52                 memset(ret, 0, size);
  53         return ret;
  54 }
  55 static inline void free_percpu(const void *ptr)
  56 {
  57         kfree(ptr);
  58 }
  59
  60 #endif /* CONFIG_SMP */
  61
  62 /* Simple wrapper for the common case: zeros memory. */
  63 #define alloc_percpu(type)      ((type *)(__alloc_percpu(sizeof(type))))
  64
  65 #endif /* __LINUX_PERCPU_H */