Linux 核心--16.Linux数据结构

第十五章　Linux核心数据结构

本章列出了Linux实用的主要数据结构。

block_dev_struct
此结构用于向核心登记块设备，它还被buffer　cache实用。所有此类结构都位于blk_dev数组中。

struct　blk_dev_struct　{
void　(*request_fn)(void);
struct　request　*　current_request;
struct　request　plug;
struct　tq_struct　plug_tq;
};

buffer_head
此结构包含关于buffer　cache中一块缓存的信息。

/*　bh　state　bits　*/
#define　BH_Uptodate0　/*　1　if　the　buffer　contains　valid　data*/
#define　BH_Dirty　1　/*　1　if　the　buffer　is　dirty　*/
#define　BH_Lock2　/*　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_aged5　/*　1　if　the　buffer　has　been　aged　(aging)*/
#define　BH_Protected　6　/*　1　if　the　buffer　is　protected　*/
#define　BH_FreeOnIO7　/*　1　to　discard　the　buffer_head　after　IO*/

struct　buffer_head　{
/*　First　cache　line:　*/
unsigned　longb_blocknr;/*　block　number　*/
kdev_t　b_dev;/*　device　(B_FREE　=　free)　*/
kdev_t　b_rdev;　/*　Real　device*/
unsigned　longb_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　longb_state;/*　buffer　state　bitmap　(above)*/
struct　buffer_head　*b_next_free;
unsigned　int　b_count;/*　users　using　this　block　*/
unsigned　longb_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　longb_flushtime;/*　Time　when　this　(dirty)　buffer
*　should　be　written*/
unsigned　longb_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
系统中每个网络设备都用一个设备数据结构来表示。

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　charstart,　/*　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　shortflags;　/*　interface　flags　(BSD)*/
unsigned　shortfamily;/*　address　family　ID*/
unsigned　shortmetric;/*　routing　metric　*/
unsigned　shortmtu;　/*　MTU　value*/
unsigned　shorttype;/*　hardware　type*/
unsigned　shorthard_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　shortpa_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
此结构被块设备和字符设备用来向核心登记（包含设备名称以及可对此设备进行的文件操作）。chrdevs和blkdevs　中的每个有效分别表示一个字符设备和块设备。

struct　device_struct　{
const　char　*　name;
struct　file_operations　*　fops;
};

file
每个打开的文件、套接口都用此结构表示。

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　*/
};

files_struct
描叙被某进程打开的所有文件。

struct　files_struct　{
int　count;
fd_set　close_on_exec;
fd_set　open_fds;
struct　file　*　fd[NR_OPEN];
};

fs_struct

struct　fs_struct　{
int　count;
unsigned　short　umask;
struct　inode　*　root,　*　pwd;
};

gendisk
包含关于某个硬盘的信息。用于磁盘初始化与分区检查时。

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
此VFS　inode结构描叙磁盘上一个文件或目录的信息。

struct　inode　{
kdev_t　i_dev;
unsigned　longi_ino;
umode_ti_mode;
nlink_ti_nlink;
uid_ti_uid;
gid_ti_gid;
kdev_t　i_rdev;
off_ti_size;
time_t　i_atime;
time_t　i_mtime;
time_t　i_ctime;
unsigned　longi_blksize;
unsigned　longi_blocks;
unsigned　longi_version;
unsigned　longi_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　chari_lock;
unsigned　chari_dirt;
unsigned　chari_pipe;
unsigned　chari_sock;
unsigned　chari_seek;
unsigned　chari_update;
unsigned　short　i_writecount;
union　{
struct　pipe_inode_info　pipe_i;
struct　minix_inode_infominix_i;
struct　ext_inode_infoext_i;
struct　ext2_inode_info　ext2_i;
struct　hpfs_inode_info　hpfs_i;
struct　msdos_inode_infomsdos_i;
struct　umsdos_inode_info　umsdos_i;
struct　iso_inode_infoisofs_i;
struct　nfs_inode_infonfs_i;
struct　xiafs_inode_infoxiafs_i;
struct　sysv_inode_info　sysv_i;
struct　affs_inode_info　affs_i;
struct　ufs_inode_infoufs_i;
struct　socketsocket_i;
void　*generic_ip;
}　u;
};

ipc_perm
此结构描叙对一个系统V　IPC对象的存取权限。

struct　ipc_perm
{
key_tkey;
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
用来描叙系统的中断处理过程。

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
用来表示可被Linux理解的二进制文件格式。

struct　linux_binfmt　{
struct　linux_binfmt　*　next;
long　*use_count;
int　(*load_binary)(struct　linux_binprm　*,　structpt_regs　*　regs);
int　(*load_shlib)(int　fd);
int　(*core_dump)(long　signr,　struct　pt_regs　*　regs);
};

mem_map_t
用来保存每个物理页面的信息。

typedef　struct　page　{
/*　these　must　be　first　(free　area　handling)　*/
struct　page*next;
struct　page*prev;
struct　inode　*inode;
unsigned　longoffset;
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　longswap_unlock_entry;
unsigned　longmap_nr;/*　page->map_nr　==　page　-　mem_map　*/
}　mem_map_t;

mm_struct
用来描叙某任务或进程的虚拟内存。

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
表示系统中的一个PCI总线。

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　charnumber;　/*　bus　number　*/
unsigned　charprimary;/*　number　of　primary　bridge　*/
unsigned　charsecondary;/*　number　of　secondary　bridge　*/
unsigned　charsubordinate;/*　max　number　of　subordinate　buses　*/
};

pci_dev
表示系统中的每个PCI设备，包括PCI-PCI和PCI-PCI桥接器。

/*
　*　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　intdevfn;　/*　encoded　device　&　function　index　*/
unsigned　shortvendor;
unsigned　shortdevice;
unsigned　intclass;　/*　3　bytes:　(base,sub,prog-if)　*/
unsigned　intmaster　:　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　charirq;/*　irq　generated　by　this　device　*/
};

request
被用来向系统的块设备发送请求。它总是向buffer　cache读出或写入数据块。

struct　request　{
volatile　int　rq_status;
#define　RQ_INACTIVE(-1)
#define　RQ_ACTIVE1
#define　RQ_SCSI_BUSY　0xffff
#define　RQ_SCSI_DONE　0xfffe
#define　RQ_SCSI_DISCONNECTING0xffe0

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
用来描叙向某个IP主机发送包的路由信息。此结构在IP路由cache内部实用。

struct　rtable
{
struct　rtable　*rt_next;
__u32　rt_dst;
__u32　rt_src;
__u32　rt_gateway;
atomic_trt_refcnt;
atomic_trt_use;
unsigned　long　rt_window;
atomic_trt_lastuse;
struct　hh_cache　*rt_hh;
struct　device　*rt_dev;
unsigned　shortrt_flags;
unsigned　shortrt_mtu;
unsigned　shortrt_irtt;
unsigned　char　rt_tos;
};

semaphore
保护临界区数据结构和代码信号灯。

struct　semaphore　{
int　count;
int　waking;
int　lock　;/*　to　make　waking　testing　atomic　*/
struct　wait_queue　*wait;
};

sk_buff
用来描叙在协议层之间交换的网络数据。

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　timevalstamp;　/*　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_BROADCAST1/*　To　all*/
#define　PACKET_MULTICAST2/*　To　group*/
#define　PACKET_OTHERHOST3/*　To　someone　else　*/
unsigned　shortusers;　/*　User　count　-　see　datagram.c,tcp.c　*/
unsigned　shortprotocol;/*　Packet　protocol　from　driver.*/
unsigned　inttruesize;/*　Buffer　size　*/
atomic_tcount;　/*　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
包含BSD套接口的协议相关信息。例如对于一个INET（Internet　Address　Domain）套接口此数据结构　包含TCP/IP和UDP/IP信息。

struct　sock
{
/*　This　must　be　first.　*/
struct　sock　*sklist_next;
struct　sock　*sklist_prev;

struct　options*opt;
atomic_twmem_alloc;
atomic_trmem_alloc;
unsigned　long　allocation;　/*　Allocation　mode　*/
__u32　write_seq;
__u32　sent_seq;
__u32　acked_seq;
__u32　copied_seq;
__u32　rcv_ack_seq;
unsigned　shortrcv_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;
longretransmits;
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　shortmax_unacked;
unsigned　shortwindow;
__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　longato;/*　ack　timeout　*/
volatile　unsigned　longlrcvtime;　/*　jiffies　at　last　data　rcv　*/
volatile　unsigned　longidletime;　/*　jiffies　at　last　rcv　*/
unsigned　intbytes_rcv;
/*
　*mss　is　min(mtu,　max_window)
　*/
unsigned　shortmtu;/*　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　intssthresh;
unsigned　shortnum;
volatile　unsigned　short　cong_window;
volatile　unsigned　short　cong_count;
volatile　unsigned　short　packets_out;
volatile　unsigned　short　shutdown;
volatile　unsigned　longrtt;
volatile　unsigned　longmdev;
volatile　unsigned　longrto;

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　charstate;
unsigned　char　ack_backlog;
unsigned　char　max_ack_backlog;
unsigned　char　priority;
unsigned　char　debug;
int　rcvbuf;
int　sndbuf;
unsigned　shorttype;
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_optaf_ipx;
#endif
#ifdef　CONFIG_INET
struct　inet_packet_optaf_packet;
#ifdef　CONFIG_NUTCP
struct　tcp_optaf_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　*/
charip_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).
　*/
inttimeout;　/*　What　are　we　waiting　for?　*/
struct　timer_listtimer;　/*　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
包含BSD套接口的信息。它不独立存在，一般位于一个VFS　inode结构中。

struct　socket　{
shorttype;　/*　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
用来描叙系统中的进程或任务。

struct　task_struct　{
/*　these　are　hardcoded　-　don"t　touch　*/
volatile　longstate;/*　-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　longsaved_kernel_stack;
unsigned　longkernel_stack_page;
intexit_code,　exit_signal;
/*　???　*/
unsigned　longpersonality;
intdumpable:1;
intdid_exec:1;
intpid;
intpgrp;
inttty_old_pgrp;
intsession;
/*　boolean　value　for　session　group　leader　*/
intleader;
intgroups[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　longtimeout,　policy,　rt_priority;
unsigned　longit_real_value,　it_prof_value,　it_virt_value;
unsigned　longit_real_incr,　it_prof_incr,　it_virt_incr;
struct　timer_listreal_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　longmin_flt,　maj_flt,　nswap,　cmin_flt,　cmaj_flt,　cnswap;
int　swappable:1;
unsigned　longswap_address;
unsigned　longold_maj_flt;/*　old　value　of　maj_flt　*/
unsigned　longdec_flt;/*　page　fault　count　of　the　last　time　*/
unsigned　longswap_cnt;　/*　number　of　pages　to　swap　on　next　pass　*/
/*　limits　*/
struct　rlimitrlim[RLIM_NLIMITS];
unsigned　short　used_math;
char　comm[16];
/*　file　system　info　*/
intlink_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__
intprocessor;
intlast_processor;
intlock_depth;　/*　Lock　depth.
We　can　context　switch　in　and　out
of　holding　a　syscall　kernel　lock...　*/
#endif
};

timer_list
用来为进程实现实时时钟。

struct　timer_list　{
struct　timer_list　*next;
struct　timer_list　*prev;
unsigned　long　expires;
unsigned　long　data;
void　(*function)(unsigned　long);
};

tq_struct
每个任务队列结构（tq_struct）包含着已经排队的任务信息。它被设备驱动用来描叙那些无需立刻　执行的任务。

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
表示某进程的一个虚拟内存区域。

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　*/
};