Linux内核全局变量总结


1.current指针
各个平台、各个内核版本中current的实现可能不同；但原理是一样的。该指针一般定义在具体平台的current.h头文件中，类型为struct task_struct：

arch/arm/include/asm/current.h

#define current (get_current())    
static inline struct task_struct *get_current(void)

include/Linux/sched.h

struct task_struct {    
  ......    
  struct thread_info *thread_info;    
  struct list_head tasks;    
  pid_t pid;    
  pid_t tgid;    
  uid_t uid,euid,suid,fsuid;    
  gid_t gid,egid,sgid,fsgid;    
  struct fs_struct *fs;  
  struct files_struct *files;    
  ......    
}




2.jiffies系统开机后“滴答”数
include/linux/jiffies.h

extern u64 __jiffy_data jiffies_64;  
extern unsigned long volatile __jiffy_data jiffies;




3.HZ、tick系统晶振主频，平台相关
arch/arm/include/asm/param.h

#ifdef __KERNEL__  
# define HZ             CONFIG_HZ       /* Internal kernel timer frequency */  
# define USER_HZ        100             /* User interfaces are in "ticks" */  
# define CLOCKS_PER_SEC (USER_HZ)       /* like times() */  
#else  
# define HZ             100  
#endif

include/linux/timex.h
extern unsigned long tick_usec;         /* USER_HZ period (usec) */  
extern unsigned long tick_nsec;         /* ACTHZ   period (nsec) */