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 /* Must be an lvalue. */
  15 #define get_cpu_var(var) (*({ preempt_disable(); &__get_cpu_var(var); }))
  16 #define put_cpu_var(var) preempt_enable()
  17
  18 #ifdef CONFIG_SMP
  19
  20 struct percpu_data {
  21         void *ptrs[NR_CPUS];
  22 };
  23
  24 /*
  25  * Use this to get to a cpu's version of the per-cpu object allocated using
  26  * alloc_percpu.  Non-atomic access to the current CPU's version should
  27  * probably be combined with get_cpu()/put_cpu().
  28  */
  29 #define per_cpu_ptr(ptr, cpu)                   \
  30 ({                                              \
  31         struct percpu_data *__p = (struct percpu_data *)~(unsigned long)(ptr); \
  32         (__typeof__(ptr))__p->ptrs[(cpu)];      \
  33 })
  34
  35 extern void *__alloc_percpu(size_t size);
  36 extern void free_percpu(const void *);
  37
  38 #else /* CONFIG_SMP */
  39
  40 #define per_cpu_ptr(ptr, cpu) ({ (void)(cpu); (ptr); })
  41
  42 static inline void *__alloc_percpu(size_t size)
  43 {
  44         void *ret = kmalloc(size, GFP_KERNEL);
  45         if (ret)
  46                 memset(ret, 0, size);
  47         return ret;
  48 }
  49 static inline void free_percpu(const void *ptr)
  50 {
  51         kfree(ptr);
  52 }
  53
  54 #endif /* CONFIG_SMP */
  55
  56 /* Simple wrapper for the common case: zeros memory. */
  57 #define alloc_percpu(type)      ((type *)(__alloc_percpu(sizeof(type))))
  58
  59 #endif /* __LINUX_PERCPU_H */