task_struct解析

task_struct是Linux内核的一种数据结构，它用task_struct结构体来描述进程的信息。下面来剖析一下进程中保存的主要的信息有哪些？

struct task_struct {//进程的运行时状态volatile long state;    /* -1 unrunnable, 0 runnable, >0 stopped */void *stack;   atomic_t usage;//进程当前的状态/*0x00000002表示进程正在被创建；0x00000004表示进程正准备退出；0x00000040 表示此进程被fork出，但是并没有执行exec；0x00000400表示此进程由于其他进程发送相关信号而被杀死 。*/unsigned int flags;     /* per process flags, defined below */unsigned int ptrace;int on_rq;//表示此进程的运行优先级，prio表示动态优先级，根据static_prio和交互性奖罚算出，static_prio是进程的静态优先级，在进程创建时确定，范围从-20到19，越小优先级越高。int prio, static_prio, normal_prio;//进程的运行优先级unsigned int rt_priority;//list_head结构体struct list_head tasks;//mm_struct结构体，描述了进程内存的相关情况struct mm_struct *mm, *active_mm;/* per-thread vma caching */u32 vmacache_seqnum;struct vm_area_struct *vmacache[VMACACHE_SIZE];/* task state *///进程的状态参数int exit_state;int exit_code, exit_signal;//父进程退出后信号被发送int pdeath_signal;  /*  The signal sent when the parent dies  */ /* scheduler bits, serialized by scheduler locks */unsigned sched_reset_on_fork:1;unsigned sched_contributes_to_load:1;unsigned sched_migrated:1;unsigned sched_remote_wakeup:1;unsigned :0; /* force alignment to the next boundary *//* unserialized, strictly 'current' */unsigned in_execve:1; /* bit to tell LSMs we're in execve */unsigned in_iowait:1;struct restart_block restart_block;//进程号pid_t pid;//进程组号pid_t tgid;//进程的亲身父亲struct task_struct __rcu *real_parent; /* real parent process *///进程的现在的父亲，可能为继父struct task_struct __rcu *parent; /* recipient of SIGCHLD, wait4() reports *///进程的孩子链表struct list_head children;      /* list of my children *///进程兄弟的链表struct list_head sibling;       /* linkage in my parent's children list *///主线程的进程描述符struct task_struct *group_leader;       /* threadgroup leader *//* PID/PID hash table linkage. */struct pid_link pids[PIDTYPE_MAX];//该进程的所有线程链表struct list_head thread_group;struct list_head thread_node;//该进程使用cpu时间的信息，utime是在用户态下执行的时间，stime是在内核态下执行的时间。cputime_t utime, stime;cputime_t gtime;struct prev_cputime prev_cputime;//启动时间，，只是时间基准不一样u64 start_time;         /* monotonic time in nsec */u64 real_start_time;    /* boot based time in nsec */struct task_cputime cputime_expires;//list_head的CPU时间struct list_head cpu_timers[3];//保存进程名字的数组，一般数组大小为15位char comm[TASK_COMM_LEN];/* file system info *///文件系统信息struct nameidata *nameidata;/* 文件系统信息计数*/int link_count, total_link_count;/* filesystem information *///文件系统相关信息结构体struct fs_struct *fs;/* open file information *///打开文件信息的结构体struct files_struct *files;/* namespaces */struct nsproxy *nsproxy;/* signal handlers *///信号相关信息的句柄struct signal_struct *signal;struct sighand_struct *sighand;struct callback_head *task_works;struct audit_context *audit_context;struct seccomp seccomp;/* Thread group tracking */u32 parent_exec_id;u32 self_exec_id;/* journalling filesystem info */void *journal_info;/* VM state */struct reclaim_state *reclaim_state;struct backing_dev_info *backing_dev_info;struct io_context *io_context;unsigned long ptrace_message;siginfo_t *last_siginfo; /* For ptrace use.  *//** time slack values; these are used to round up poll() and* select() etc timeout values. These are in nanoseconds.*///松弛时间值，用来记录select和poll的超时时间，单位为nsu64 timer_slack_ns;u64 default_timer_slack_ns;/* CPU-specific state of this task *///该进程在特定CPU下的状态struct thread_struct thread;};