Linux Data Structures （ Linux 数据结构）
本附录列出了本书中描述的 Linux 使用的主要的数据结构。为了在页面上访得下，它们经过了少量的编辑。
Block_dev_struct
block_dev_struct 数据结构用于登记可用的块设备，让 buffer cache 使用。它们放在 blk_dev 向量表中。
参见 include/linux/blkdev.h
struct blk_dev_struct {
void (*request_fn)(void);
struct request * current_request;
struct request plug;
struct tq_struct plug_tq;
} ;
buffer_head
buffer_head 数据结构存放 buffer cache 中一个块缓冲区的信息。
参见 include/linux/fs.h
* bh state bits */
#define BH_Uptodate 0 /* 1 if the buffer contains valid data */
#define BH_Dirty 1 /* 1 if the buffer is dirty */
#define BH_Lock 2 /* 1 if the buffer is locked */
#define BH_Req 3 /* 0 if the buffer has been invalidated */
#define BH_Touched 4 /* 1 if the buffer has been touched (aging) */
#define BH_Has_aged 5 /* 1 if the buffer has been aged (aging) */
#define BH_Protected 6 /* 1 if the buffer is protected */
#define BH_FreeOnIO 7 /* 1 to discard the buffer_head after IO */
struct buffer_head {
/* First cache line: */
unsigned long b_blocknr; /* block number */
kdev_t b_dev; /* device (B_FREE = free) */
kdev_t b_rdev; /* Real device */
unsigned long b_rsector; /* Real buffer location on disk */
struct buffer_head *b_next; /* Hash queue list */
struct buffer_head *b_this_page; /* circular list of buffers in one
page */
/* Second cache line: */
unsigned long b_state; /* buffer state bitmap (above) */
struct buffer_head *b_next_free;
unsigned int b_count; /* users using this block */
unsigned long b_size; /* block size */
/* Non-performance-critical data follows. */
char *b_data; /* pointer to data block */
unsigned int b_list; /* List that this buffer appears */
unsigned long b_flushtime; /* Time when this (dirty) buffer
* should be written */
unsigned long b_lru_time; /* Time when this buffer was
* last used. */
struct wait_queue *b_wait;
struct buffer_head *b_prev; /* doubly linked hash list */
struct buffer_head *b_prev_free; /* doubly linked list of buffers */
struct buffer_head *b_reqnext; /* request queue */
} ;
device
系统中的每一个网络设备都用一个 device 数据结构表示
参见 include/linux/netdevice.h
struct device
{
/*
* This is the first field of the "visible" part of this structure
* (i.e. as seen by users in the "Space.c" file). It is the name
* the interface.
*/
char *name;
/* I/O specific fields */
unsigned long rmem_end; /* shmem "recv" end */
unsigned long rmem_start; /* shmem "recv" start */
unsigned long mem_end; /* shared mem end */
unsigned long mem_start; /* shared mem start */
unsigned long base_addr; /* device I/O address */
unsigned char irq; /* device IRQ number */
/* Low-level status flags. */
volatile unsigned char start, /* start an operation */
interrupt; /* interrupt arrived */
unsigned long tbusy; /* transmitter busy */
struct device *next;
/* The device initialization function. Called only once. */
int (*init)(struct device *dev);
/* Some hardware also needs these fields, but they are not part of
the usual set specified in Space.c. */
unsigned char if_port; /* Selectable AUI,TP, */
unsigned char dma; /* DMA channel */
struct enet_statistics* (*get_stats)(struct device *dev);
/*
* This marks the end of the "visible" part of the structure. All
* fields hereafter are internal to the system, and may change at
* will (read: may be cleaned up at will).
*/
/* These may be needed for future network-power-down code. */
unsigned long trans_start; /* Time (jiffies) of
last transmit */
unsigned long last_rx; /* Time of last Rx */
unsigned short flags; /* interface flags (BSD)*/
unsigned short family; /* address family ID */
unsigned short metric; /* routing metric */
unsigned short mtu; /* MTU value */
unsigned short type; /* hardware type */
unsigned short hard_header_len; /* hardware hdr len */
void *priv; /* private data */
/* Interface address info. */
unsigned char broadcast[MAX_ADDR_LEN];
unsigned char pad;
unsigned char dev_addr[MAX_ADDR_LEN];
unsigned char addr_len; /* hardware addr len */
unsigned long pa_addr; /* protocol address */
unsigned long pa_brdaddr; /* protocol broadcast addr*/
unsigned long pa_dstaddr; /* protocol P-P other addr*/
unsigned long pa_mask; /* protocol netmask */
unsigned short pa_alen; /* protocol address len */
struct dev_mc_list *mc_list; /* M'cast mac addrs */
int mc_count; /* No installed mcasts */
struct ip_mc_list *ip_mc_list; /* IP m'cast filter chain */
__u32 tx_queue_len; /* Max frames per queue */
/* For load balancing driver pair support */
unsigned long pkt_queue; /* Packets queued */
struct device *slave; /* Slave device */
struct net_alias_info *alias_info; /* main dev alias info */
struct net_alias *my_alias; /* alias devs */
/* Pointer to the interface buffers. */
struct sk_buff_head buffs[DEV_NUMBUFFS];
/* Pointers to interface service routines. */
int (*open)(struct device *dev);
int (*stop)(struct device *dev);
int (*hard_start_xmit) (struct sk_buff *skb,
struct device *dev);
int (*hard_header) (struct sk_buff *skb,
struct device *dev,
unsigned short type,
void *daddr,
void *saddr,
unsigned len);
int (*rebuild_header)(void *eth,
struct device *dev,
unsigned long raddr,
struct sk_buff *skb);
void (*set_multicast_list)(struct device *dev);
int (*set_mac_address)(struct device *dev,
void *addr);
int (*do_ioctl)(struct device *dev,
struct ifreq *ifr,
int cmd);
int (*set_config)(struct device *dev,
struct ifmap *map);
void (*header_cache_bind)(struct hh_cache **hhp,
struct device *dev,
unsigned short htype,
__u32 daddr);
void (*header_cache_update)(struct hh_cache *hh,
struct device *dev,
unsigned char * haddr);
int (*change_mtu)(struct device *dev,
int new_mtu);
struct iw_statistics* (*get_wireless_stats)(struct device *dev);
} ;
device_struct
device_struct 数据结构用于登记字符和块设备（存放这个设备的名称和可能进行的文件操作）。 Chrdevs 和 blkdevs 向量表中的每一个有效的成员都分别代表一个字符或块设备。
参见 fs/devices.c
struct device_struct {
const char * name;
struct file_operations * fops;
} ;
file
每一个打开的文件、 socket 等等都用一个 file 数据结构代表
参见 include/linux/fs.h
struct file {
mode_t f_mode;
loff_t f_pos;
unsigned short f_flags;
unsigned short f_count;
unsigned long f_reada, f_ramax, f_raend, f_ralen, f_rawin;
struct file *f_next, *f_prev;
int f_owner; /* pid or -pgrp where SIGIO should be sent */
struct inode * f_inode;
struct file_operations * f_op;
unsigned long f_version;
void *private_data; /* needed for tty driver, and maybe others */
} ;
file_struct
file_struct 数据结构描述了一个进程打开的文件
参见 include/linux/sched.h
struct files_struct {
int count;
fd_set close_on_exec;
fd_set open_fds;
struct file * fd[NR_OPEN];
} ;
fs_struct
参见 include/linux/sched.h
struct fs_struct {
int count;
unsigned short umask;
struct inode * root, * pwd;
} ;
gendisk
gendisk 数据结构存放硬盘的信息。用在初始化过程中找到磁盘，探测分区的时候
参见 include/linux/genhd.h
struct hd_struct {
long start_sect;
long nr_sects;
} ;
struct gendisk {
int major; /* major number of driver */
const char *major_name; /* name of major driver */
int minor_shift; /* number of times minor is shifted to
get real minor */
int max_p; /* maximum partitions per device */
int max_nr; /* maximum number of real devices */
void (*init)(struct gendisk *);
/* Initialization called before we
do our thing */
struct hd_struct *part; /* partition table */
int *sizes; /* device size in blocks, copied to
blk_size[] */
int nr_real; /* number of real devices */
void *real_devices; /* internal use */
struct gendisk *next;
} ;
inode
VFS inode 数据结构存放磁盘上的一个文件或目录的信息
参见 include/linux/fs.h
struct inode {
kdev_t i_dev;
unsigned long i_ino;
umode_t i_mode;
nlink_t i_nlink;
uid_t i_uid;
gid_t i_gid;
kdev_t i_rdev;
off_t i_size;
time_t i_atime;
time_t i_mtime;
time_t i_ctime;
unsigned long i_blksize;
unsigned long i_blocks;
unsigned long i_version;
unsigned long i_nrpages;
struct semaphore i_sem;
struct inode_operations *i_op;
struct super_block *i_sb;
struct wait_queue *i_wait;
struct file_lock *i_flock;
struct vm_area_struct *i_mmap;
struct page *i_pages;
struct dquot *i_dquot[MAXQUOTAS];
struct inode *i_next, *i_prev;
struct inode *i_hash_next, *i_hash_prev;
struct inode *i_bound_to, *i_bound_by;
struct inode *i_mount;
unsigned short i_count;
unsigned short i_flags;
unsigned char i_lock;
unsigned char i_dirt;
unsigned char i_pipe;
unsigned char i_sock;
unsigned char i_seek;
unsigned char i_update;
unsigned short i_writecount;
union {
struct pipe_inode_info pipe_i;
struct minix_inode_info minix_i;
struct ext_inode_info ext_i;
struct ext2_inode_info ext2_i;
struct hpfs_inode_info hpfs_i;
struct msdos_inode_info msdos_i;
struct umsdos_inode_info umsdos_i;
struct iso_inode_info isofs_i;
struct nfs_inode_info nfs_i;
struct xiafs_inode_info xiafs_i;
struct sysv_inode_info sysv_i;
struct affs_inode_info affs_i;
struct ufs_inode_info ufs_i;
struct socket socket_i;
void *generic_ip;
} u;
} ;
ipc_perm
ipc_perm 数据结构描述一个系统 V IPC 对象的访问权限
参见 include/linux/ipc.h
struct ipc_perm
{
key_t key;
ushort uid; /* owner euid and egid */
ushort gid;
ushort cuid; /* creator euid and egid */
ushort cgid;
ushort mode; /* access modes see mode flags below */
ushort seq; /* sequence number */
} ;
irqaction
irqaction 数据结构描述系统的中断处理程序
参见 include/linux/interrupt.h
struct irqaction {
void (*handler)(int, void *, struct pt_regs *);
unsigned long flags;
unsigned long mask;
const char *name;
void *dev_id;
struct irqaction *next;
} ;
linux_binfmt
Linux 理解的每一个二进制文件格式都用一个 linux_binfmt 数据结构表示
参见 include/linux/binfmt.h
struct linux_binfmt {
struct linux_binfmt * next;
long *use_count;
int (*load_binary)(struct linux_binprm *, struct pt_regs * regs);
int (*load_shlib)(int fd);
int (*core_dump)(long signr, struct pt_regs * regs);
} ;
mem_map_t
mem_map_t 数据结构（也叫做 page ）用于存放每一个物理内存页的信息
参见 include/linux/mm.h
typedef struct page {
/* these must be first (free area handling) */
struct page *next;
struct page *prev;
struct inode *inode;
unsigned long offset;
struct page *next_hash;
atomic_t count;
unsigned flags; /* atomic flags, some possibly
updated asynchronously */
unsigned dirty:16,
age:8;
struct wait_queue *wait;
struct page *prev_hash;
struct buffer_head *buffers;
unsigned long swap_unlock_entry;
unsigned long map_nr; /* page->map_nr == page - mem_map */
} mem_map_t;
mm struct
mm_struct 数据结构用于描述一个任务或进程的虚拟内存
参见 include/linux/sched.h
struct mm_struct {
int count;
pgd_t * pgd;
unsigned long context;
unsigned long start_code, end_code, start_data, end_data;
unsigned long start_brk, brk, start_stack, start_mmap;
unsigned long arg_start, arg_end, env_start, env_end;
unsigned long rss, total_vm, locked_vm;
unsigned long def_flags;
struct vm_area_struct * mmap;
struct vm_area_struct * mmap_avl;
struct semaphore mmap_sem;
} ;
pci_bus
系统中的每一个 PCI 总线用一个 pci_bus 数据结构表示
参见 include/linux/pci.h
struct pci_bus {
struct pci_bus *parent; /* parent bus this bridge is on */
struct pci_bus *children; /* chain of P2P bridges on this bus */
struct pci_bus *next; /* chain of all PCI buses */
struct pci_dev *self; /* bridge device as seen by parent */
struct pci_dev *devices; /* devices behind this bridge */
void *sysdata; /* hook for sys-specific extension */
unsigned char number; /* bus number */
unsigned char primary; /* number of primary bridge */
unsigned char secondary; /* number of secondary bridge */
unsigned char subordinate; /* max number of subordinate buses */
} ;
pci_dev
系统中的每一个 PCI 设备，包括 PCI-PCI 和 PCI-ISA 桥设备都用一个 pci_dev 数据结构代表
参见 include/linux/pci.h
/*
* There is one pci_dev structure for each slot-number/function-number
* combination:
*/
struct pci_dev {
struct pci_bus *bus; /* bus this device is on */
struct pci_dev *sibling; /* next device on this bus */
struct pci_dev *next; /* chain of all devices */
void *sysdata; /* hook for sys-specific extension */
unsigned int devfn; /* encoded device & function index */
unsigned short vendor;
unsigned short device;
unsigned int class; /* 3 bytes: (base,sub,prog-if) */
unsigned int master : 1; /* set if device is master capable */
/*
* In theory, the irq level can be read from configuration
* space and all would be fine. However, old PCI chips don't
* support these registers and return 0 instead. For example,
* the Vision864-P rev 0 chip can uses INTA, but returns 0 in
* the interrupt line and pin registers. pci_init()
* initializes this field with the value at PCI_INTERRUPT_LINE
* and it is the job of pcibios_fixup() to change it if
* necessary. The field must not be 0 unless the device
* cannot generate interrupts at all.
*/
unsigned char irq; /* irq generated by this device */
} ;
request
request 用于向系统中的块设备发出请求。请求都是从 / 向 buffer cache 读 / 写数据块
参见 include/linux/blkdev.h
struct request {
volatile int rq_status;
#define RQ_INACTIVE (-1)
#define RQ_ACTIVE 1
#define RQ_SCSI_BUSY 0xffff
#define RQ_SCSI_DONE 0xfffe
#define RQ_SCSI_DISCONNECTING 0xffe0
kdev_t rq_dev;
int cmd; /* READ or WRITE */
int errors;
unsigned long sector;
unsigned long nr_sectors;
unsigned long current_nr_sectors;
char * buffer;
struct semaphore * sem;
struct buffer_head * bh;
struct buffer_head * bhtail;
struct request * next;
} ;
rtable
每一个 rtable 数据结构都存放向一个 IP 主机发送报文的路由的信息。 Rtable 数据结构在 IP route 缓存中使用。
参见 include/net/route.h
struct rtable
{
struct rtable *rt_next;
__u32 rt_dst;
__u32 rt_src;
__u32 rt_gateway;
atomic_t rt_refcnt;
atomic_t rt_use;
unsigned long rt_window;
atomic_t rt_lastuse;
struct hh_cache *rt_hh;
struct device *rt_dev;
unsigned short rt_flags;
unsigned short rt_mtu;
unsigned short rt_irtt;
unsigned char rt_tos;
} ;
semaphore
信号灯用于保护重要数据结构和代码区域。
参见 include/asm/semaphore.h
struct semaphore {
int count;
int waking;
int lock ; /* to make waking testing atomic */
struct wait_queue *wait;
} ;
sk_buff
sk_buff 数据结构当网络数据在协议层之间移动的过程中描述网络数据。
参见 include/linux/sk_buff.h
struct sk_buff
{
struct sk_buff *next; /* Next buffer in list */
struct sk_buff *prev; /* Previous buffer in list */
struct sk_buff_head *list; /* List we are on */
int magic_debug_cookie;
struct sk_buff *link3; /* Link for IP protocol level buffer chains */
struct sock *sk; /* Socket we are owned by */
unsigned long when; /* used to compute rtt's */
struct timeval stamp; /* Time we arrived */
struct device *dev; /* Device we arrived on/are leaving by */
union
{
struct tcphdr *th;
struct ethhdr *eth;
struct iphdr *iph;
struct udphdr *uh;
unsigned char *raw;
/* for passing file handles in a unix domain socket */
void *filp;
} h;
union
{
/* As yet incomplete physical layer views */
unsigned char *raw;
struct ethhdr *ethernet;
} mac;
struct iphdr *ip_hdr; /* For IPPROTO_RAW */
unsigned long len; /* Length of actual data */
unsigned long csum; /* Checksum */
__u32 saddr; /* IP source address */
__u32 daddr; /* IP target address */
__u32 raddr; /* IP next hop address */
__u32 seq; /* TCP sequence number */
__u32 end_seq; /* seq [+ fin] [+ syn] + datalen */
__u32 ack_seq; /* TCP ack sequence number */
unsigned char proto_priv[16];
volatile char acked, /* Are we acked ? */
used, /* Are we in use ? */
free, /* How to free this buffer */
arp; /* Has IP/ARP resolution finished */
unsigned char tries, /* Times tried */
lock, /* Are we locked ? */
localroute, /* Local routing asserted for this frame */
pkt_type, /* Packet class */
pkt_bridged, /* Tracker for bridging */
ip_summed; /* Driver fed us an IP checksum */
#define PACKET_HOST 0 /* To us */
#define PACKET_BROADCAST 1 /* To all */
#define PACKET_MULTICAST 2 /* To group */
#define PACKET_OTHERHOST 3 /* To someone else */
unsigned short users; /* User count - see datagram.c,tcp.c */
unsigned short protocol; /* Packet protocol from driver. */
unsigned int truesize; /* Buffer size */
atomic_t count; /* reference count */
struct sk_buff *data_skb; /* Link to the actual data skb */
unsigned char *head; /* Head of buffer */
unsigned char *data; /* Data head pointer */
unsigned char *tail; /* Tail pointer */
unsigned char *end; /* End pointer */
void (*destructor)(struct sk_buff *); /* Destruct function */
__u16 redirport; /* Redirect port */
} ;
sock
每一个 sock 数据结构都存放一个 BSD socket 中和协议相关的信息。例如，对于一个 INET socket ，这个数据结构会存放所有的 TCP/IP 和 UDP/IP 相关的信息
参见 include/linux/net.h
struct sock
{
/* This must be first. */
struct sock *sklist_next;
struct sock *sklist_prev;
struct options *opt;
atomic_t wmem_alloc;
atomic_t rmem_alloc;
unsigned long allocation; /* Allocation mode */
__u32 write_seq;
__u32 sent_seq;
__u32 acked_seq;
__u32 copied_seq;
__u32 rcv_ack_seq;
unsigned short rcv_ack_cnt; /* count of same ack */
__u32 window_seq;
__u32 fin_seq;
__u32 urg_seq;
__u32 urg_data;
__u32 syn_seq;
int users; /* user count */
/*
* Not all are volatile, but some are, so we
* might as well say they all are.
*/
volatile char dead,
urginline,
intr,
blog,
done,
reuse,
keepopen,
linger,
delay_acks,
destroy,
ack_timed,
no_check,
zapped,
broadcast,
nonagle,
bsdism;
unsigned long lingertime;
int proc;
struct sock *next;
struct sock **pprev;
struct sock *bind_next;
struct sock **bind_pprev;
struct sock *pair;
int hashent;
struct sock *prev;
struct sk_buff *volatile send_head;
struct sk_buff *volatile send_next;
struct sk_buff *volatile send_tail;
struct sk_buff_head back_log;
struct sk_buff *partial;
struct timer_list partial_timer;
long retransmits;
struct sk_buff_head write_queue,
receive_queue;
struct proto *prot;
struct wait_queue **sleep;
__u32 daddr;
__u32 saddr; /* Sending source */
__u32 rcv_saddr; /* Bound address */
unsigned short max_unacked;
unsigned short window;
__u32 lastwin_seq; /* sequence number when we last
updated the window we offer */
__u32 high_seq; /* sequence number when we did
current fast retransmit */
volatile unsigned long ato; /* ack timeout */
volatile unsigned long lrcvtime; /* jiffies at last data rcv */
volatile unsigned long idletime; /* jiffies at last rcv */
unsigned int bytes_rcv;
/*
* mss is min(mtu, max_window)
*/
unsigned short mtu; /* mss negotiated in the syn's */
volatile unsigned short mss; /* current eff. mss - can change */
volatile unsigned short user_mss; /* mss requested by user in ioctl */
volatile unsigned short max_window;
unsigned long window_clamp;
unsigned int ssthresh;
unsigned short num;
volatile unsigned short cong_window;
volatile unsigned short cong_count;
volatile unsigned short packets_out;
volatile unsigned short shutdown;
volatile unsigned long rtt;
volatile unsigned long mdev;
volatile unsigned long rto;
volatile unsigned short backoff;
int err, err_soft; /* Soft holds errors that don't
cause failure but are the cause
of a persistent failure not
just 'timed out' */
unsigned char protocol;
volatile unsigned char state;
unsigned char ack_backlog;
unsigned char max_ack_backlog;
unsigned char priority;
unsigned char debug;
int rcvbuf;
int sndbuf;
unsigned short type;
unsigned char localroute; /* Route locally only */
/*
* This is where all the private (optional) areas that don't
* overlap will eventually live.
*/
union
{
struct unix_opt af_unix;
#if defined(CONFIG_ATALK) || defined(CONFIG_ATALK_MODULE)
struct atalk_sock af_at;
#endif
#if defined(CONFIG_IPX) || defined(CONFIG_IPX_MODULE)
struct ipx_opt af_ipx;
#endif
#ifdef CONFIG_INET
struct inet_packet_opt af_packet;
#ifdef CONFIG_NUTCP
struct tcp_opt af_tcp;
#endif
#endif
} protinfo;
/*
* IP 'private area'
*/
int ip_ttl; /* TTL setting */
int ip_tos; /* TOS */
struct tcphdr dummy_th;
struct timer_list keepalive_timer; /* TCP keepalive hack */
struct timer_list retransmit_timer; /* TCP retransmit timer */
struct timer_list delack_timer; /* TCP delayed ack timer */
int ip_xmit_timeout; /* Why the timeout is running */
struct rtable *ip_route_cache; /* Cached output route */
unsigned char ip_hdrincl; /* Include headers ? */
#ifdef CONFIG_IP_MULTICAST
int ip_mc_ttl; /* Multicasting TTL */
int ip_mc_loop; /* Loopback */
char ip_mc_name[MAX_ADDR_LEN]; /* Multicast device name */
struct ip_mc_socklist *ip_mc_list; /* Group array */
#endif
/*
* This part is used for the timeout functions (timer.c).
*/
int timeout; /* What are we waiting for? */
struct timer_list timer; /* This is the TIME_WAIT/receive
* timer when we are doing IP
*/
struct timeval stamp;
/*
* Identd
*/
struct socket *socket;
/*
* Callbacks
*/
void (*state_change)(struct sock *sk);
void (*data_ready)(struct sock *sk,int bytes);
void (*write_space)(struct sock *sk);
void (*error_report)(struct sock *sk);
} ;
socket
每一个 socket 数据结构都存放一个 BSD socket 的信息。它不会独立存在，实际上是 VFS inode 数据结构的一部分
参见 include/linux/net.h
struct socket {
short type; /* SOCK_STREAM, ... */
socket_state state;
long flags;
struct proto_ops *ops; /* protocols do most everything */
void *data; /* protocol data */
struct socket *conn; /* server socket connected to */
struct socket *iconn; /* incomplete client conn.s */
struct socket *next;
struct wait_queue **wait; /* ptr to place to wait on */
struct inode *inode;
struct fasync_struct *fasync_list; /* Asynchronous wake up list */
struct file *file; /* File back pointer for gc */
} ;
task_struct
每一个 task_struct 描述系统中的一个任务或进程
参见 include/linux/sched.h
struct task_struct {
/* these are hardcoded - don't touch */
volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */
long counter;
long priority;
unsigned long signal;
unsigned long blocked; /* bitmap of masked signals */
unsigned long flags; /* per process flags, defined below */
int errno;
long debugreg[8]; /* Hardware debugging registers */
struct exec_domain *exec_domain;
/* various fields */
struct linux_binfmt *binfmt;
struct task_struct *next_task, *prev_task;
struct task_struct *next_run, *prev_run;
unsigned long saved_kernel_stack;
unsigned long kernel_stack_page;
int exit_code, exit_signal;
/* ??? */
unsigned long personality;
int dumpable:1;
int did_exec:1;
int pid;
int pgrp;
int tty_old_pgrp;
int session;
/* boolean value for session group leader */
int leader;
int groups[NGROUPS];
/*
* pointers to (original) parent process, youngest child, younger sibling,
* older sibling, respectively. (p->father can be replaced with
* p->p_pptr->pid)
*/
struct task_struct *p_opptr, *p_pptr, *p_cptr,
*p_ysptr, *p_osptr;
struct wait_queue *wait_chldexit;
unsigned short uid,euid,suid,fsuid;
unsigned short gid,egid,sgid,fsgid;
unsigned long timeout, policy, rt_priority;
unsigned long it_real_value, it_prof_value, it_virt_value;
unsigned long it_real_incr, it_prof_incr, it_virt_incr;
struct timer_list real_timer;
long utime, stime, cutime, cstime, start_time;
/* mm fault and swap info: this can arguably be seen as either
mm-specific or thread-specific */
unsigned long min_flt, maj_flt, nswap, cmin_flt, cmaj_flt, cnswap;
int swappable:1;
unsigned long swap_address;
unsigned long old_maj_flt; /* old value of maj_flt */
unsigned long dec_flt; /* page fault count of the last time */
unsigned long swap_cnt; /* number of pages to swap on next pass */
/* limits */
struct rlimit rlim[RLIM_NLIMITS];
unsigned short used_math;
char comm[16];
/* file system info */
int link_count;
struct tty_struct *tty; /* NULL if no tty */
/* ipc stuff */
struct sem_undo *semundo;
struct sem_queue *semsleeping;
/* ldt for this task - used by Wine. If NULL, default_ldt is used */
struct desc_struct *ldt;
/* tss for this task */
struct thread_struct tss;
/* filesystem information */
struct fs_struct *fs;
/* open file information */
struct files_struct *files;
/* memory management info */
struct mm_struct *mm;
/* signal handlers */
struct signal_struct *sig;
#ifdef __SMP__
int processor;
int last_processor;
int lock_depth; /* Lock depth.
We can context switch in and out
of holding a syscall kernel lock... */
#endif
} ;
timer_list
timer_list 数据结构用于实现进程的实时计时器。
参见 include/linux/timer.h
struct timer_list {
struct timer_list *next;
struct timer_list *prev;
unsigned long expires;
unsigned long data;
void (*function)(unsigned long);
} ;
tq_struct
每一个任务队列（ tq_struct ）数据结构都存放正在排队的工作的信息。通常是一个设备驱动程序需要的任务，但是不需要立即完成。
参见 include/linux/tqueue.h
struct tq_struct {
struct tq_struct *next; /* linked list of active bh's */
int sync; /* must be initialized to zero */
void (*routine)(void *); /* function to call */
void *data; /* argument to function */
} ;
vm_area_struct
每一个 vm_area_struct 数据结构描述一个进程的一个虚拟内存区
参见 include/linux/mm.h
struct vm_area_struct {
struct mm_struct * vm_mm; /* VM area parameters */
unsigned long vm_start;
unsigned long vm_end;
pgprot_t vm_page_prot;
unsigned short vm_flags;
/* AVL tree of VM areas per task, sorted by address */
short vm_avl_height;
struct vm_area_struct * vm_avl_left;
struct vm_area_struct * vm_avl_right;
/* linked list of VM areas per task, sorted by address */
struct vm_area_struct * vm_next;
/* for areas with inode, the circular list inode->i_mmap */
/* for shm areas, the circular list of attaches */
/* otherwise unused */
struct vm_area_struct * vm_next_share;
struct vm_area_struct * vm_prev_share;
/* more */
struct vm_operations_struct * vm_ops;
unsigned long vm_offset;
struct inode * vm_inode;
unsigned long vm_pte; /* shared mem */
} ;