Linux Kernel调度管理之task_struct

task_struct是进程描述符：

struct task_struct {#ifdef CONFIG_THREAD_INFO_IN_TASK/* * For reasons of header soup (see current_thread_info()), this * must be the first element of task_struct. */struct thread_info thread_info;#endifvolatile long state;进程状态/* -1 unrunnable, 0 runnable, >0 stopped */void *stack;进程内核栈atomic_t usage;unsigned int flags;/* per process flags, defined below */unsigned int ptrace;#ifdef CONFIG_SMPstruct llist_node wake_entry;int on_cpu;#ifdef CONFIG_THREAD_INFO_IN_TASKunsigned int cpu;/* current CPU */#endifunsigned int wakee_flips;unsigned long wakee_flip_decay_ts;struct task_struct *last_wakee;int wake_cpu;#endifint on_rq;int prio, static_prio, normal_prio;unsigned int rt_priority;const struct sched_class *sched_class;struct sched_entity se;struct sched_rt_entity rt;#ifdef CONFIG_CGROUP_SCHEDstruct task_group *sched_task_group;#endifstruct sched_dl_entity dl;#ifdef CONFIG_PREEMPT_NOTIFIERS/* list of struct preempt_notifier: */struct hlist_head preempt_notifiers;#endif#ifdef CONFIG_BLK_DEV_IO_TRACEunsigned int btrace_seq;#endifunsigned int policy;int nr_cpus_allowed;cpumask_t cpus_allowed;#ifdef CONFIG_PREEMPT_RCUint rcu_read_lock_nesting;union rcu_special rcu_read_unlock_special;struct list_head rcu_node_entry;struct rcu_node *rcu_blocked_node;#endif /* #ifdef CONFIG_PREEMPT_RCU */#ifdef CONFIG_TASKS_RCUunsigned long rcu_tasks_nvcsw;bool rcu_tasks_holdout;struct list_head rcu_tasks_holdout_list;int rcu_tasks_idle_cpu;#endif /* #ifdef CONFIG_TASKS_RCU */#ifdef CONFIG_SCHED_INFOstruct sched_info sched_info;#endifstruct list_head tasks;#ifdef CONFIG_SMPstruct plist_node pushable_tasks;struct rb_node pushable_dl_tasks;#endifstruct mm_struct *mm, *active_mm;/* per-thread vma caching */u32 vmacache_seqnum;struct vm_area_struct *vmacache[VMACACHE_SIZE];#if defined(SPLIT_RSS_COUNTING)struct task_rss_statrss_stat;#endif/* task state */int exit_state;int exit_code, exit_signal;int pdeath_signal;  /*  The signal sent when the parent dies  */unsigned long jobctl;/* JOBCTL_*, siglock protected *//* Used for emulating ABI behavior of previous Linux versions */unsigned int personality;/* 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;#if !defined(TIF_RESTORE_SIGMASK)unsigned restore_sigmask:1;#endif#ifdef CONFIG_MEMCGunsigned memcg_may_oom:1;#ifndef CONFIG_SLOBunsigned memcg_kmem_skip_account:1;#endif#endif#ifdef CONFIG_COMPAT_BRKunsigned brk_randomized:1;#endifunsigned long atomic_flags; /* Flags needing atomic access. */struct restart_block restart_block;pid_t pid;pid_t tgid;#ifdef CONFIG_CC_STACKPROTECTOR/* Canary value for the -fstack-protector gcc feature */unsigned long stack_canary;#endif/* * pointers to (original) parent process, youngest child, younger sibling, * older sibling, respectively.  (p->father can be replaced with * p->real_parent->pid) */struct task_struct __rcu *real_parent; /* real parent process */struct task_struct __rcu *parent; /* recipient of SIGCHLD, wait4() reports *//* * children/sibling forms the list of my natural children */struct list_head children;/* list of my children */struct list_head sibling;/* linkage in my parent's children list */struct task_struct *group_leader;/* threadgroup leader *//* * ptraced is the list of tasks this task is using ptrace on. * This includes both natural children and PTRACE_ATTACH targets. * p->ptrace_entry is p's link on the p->parent->ptraced list. */struct list_head ptraced;struct list_head ptrace_entry;/* PID/PID hash table linkage. */struct pid_link pids[PIDTYPE_MAX];struct list_head thread_group;struct list_head thread_node;struct completion *vfork_done;/* for vfork() */int __user *set_child_tid;/* CLONE_CHILD_SETTID */int __user *clear_child_tid;/* CLONE_CHILD_CLEARTID */cputime_t utime, stime, utimescaled, stimescaled;cputime_t gtime;struct prev_cputime prev_cputime;#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GENseqcount_t vtime_seqcount;unsigned long long vtime_snap;enum {/* Task is sleeping or running in a CPU with VTIME inactive */VTIME_INACTIVE = 0,/* Task runs in userspace in a CPU with VTIME active */VTIME_USER,/* Task runs in kernelspace in a CPU with VTIME active */VTIME_SYS,} vtime_snap_whence;#endif#ifdef CONFIG_NO_HZ_FULLatomic_t tick_dep_mask;#endifunsigned long nvcsw, nivcsw; /* context switch counts */u64 start_time;/* monotonic time in nsec */u64 real_start_time;/* boot based time in nsec *//* mm fault and swap info: this can arguably be seen as either mm-specific or thread-specific */unsigned long min_flt, maj_flt;struct task_cputime cputime_expires;struct list_head cpu_timers[3];/* process credentials */const struct cred __rcu *ptracer_cred; /* Tracer's credentials at attach */const struct cred __rcu *real_cred; /* objective and real subjective task * credentials (COW) */const struct cred __rcu *cred;/* effective (overridable) subjective task * credentials (COW) */char comm[TASK_COMM_LEN]; /* executable name excluding path     - access with [gs]et_task_comm (which lock       it with task_lock())     - initialized normally by setup_new_exec *//* file system info */struct nameidata *nameidata;#ifdef CONFIG_SYSVIPC/* ipc stuff */struct sysv_sem sysvsem;struct sysv_shm sysvshm;#endif#ifdef CONFIG_DETECT_HUNG_TASK/* hung task detection */unsigned long last_switch_count;#endif/* filesystem information */struct fs_struct *fs;/* open file information */struct files_struct *files;/* namespaces */struct nsproxy *nsproxy;/* signal handlers */struct signal_struct *signal;struct sighand_struct *sighand;sigset_t blocked, real_blocked;sigset_t saved_sigmask;/* restored if set_restore_sigmask() was used */struct sigpending pending;unsigned long sas_ss_sp;size_t sas_ss_size;unsigned sas_ss_flags;struct callback_head *task_works;struct audit_context *audit_context;#ifdef CONFIG_AUDITSYSCALLkuid_t loginuid;unsigned int sessionid;#endifstruct seccomp seccomp;/* Thread group tracking */   u32 parent_exec_id;   u32 self_exec_id;/* Protection of (de-)allocation: mm, files, fs, tty, keyrings, mems_allowed, * mempolicy */spinlock_t alloc_lock;/* Protection of the PI data structures: */raw_spinlock_t pi_lock;struct wake_q_node wake_q;#ifdef CONFIG_RT_MUTEXES/* PI waiters blocked on a rt_mutex held by this task */struct rb_root pi_waiters;struct rb_node *pi_waiters_leftmost;/* Deadlock detection and priority inheritance handling */struct rt_mutex_waiter *pi_blocked_on;#endif#ifdef CONFIG_DEBUG_MUTEXES/* mutex deadlock detection */struct mutex_waiter *blocked_on;#endif#ifdef CONFIG_TRACE_IRQFLAGSunsigned int irq_events;unsigned long hardirq_enable_ip;unsigned long hardirq_disable_ip;unsigned int hardirq_enable_event;unsigned int hardirq_disable_event;int hardirqs_enabled;int hardirq_context;unsigned long softirq_disable_ip;unsigned long softirq_enable_ip;unsigned int softirq_disable_event;unsigned int softirq_enable_event;int softirqs_enabled;int softirq_context;#endif#ifdef CONFIG_LOCKDEP# define MAX_LOCK_DEPTH 48ULu64 curr_chain_key;int lockdep_depth;unsigned int lockdep_recursion;struct held_lock held_locks[MAX_LOCK_DEPTH];gfp_t lockdep_reclaim_gfp;#endif#ifdef CONFIG_UBSANunsigned int in_ubsan;#endif/* journalling filesystem info */void *journal_info;/* stacked block device info */struct bio_list *bio_list;#ifdef CONFIG_BLOCK/* stack plugging */struct blk_plug *plug;#endif/* 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.  */struct task_io_accounting ioac;#if defined(CONFIG_TASK_XACCT)u64 acct_rss_mem1;/* accumulated rss usage */u64 acct_vm_mem1;/* accumulated virtual memory usage */cputime_t acct_timexpd;/* stime + utime since last update */#endif#ifdef CONFIG_CPUSETSnodemask_t mems_allowed;/* Protected by alloc_lock */seqcount_t mems_allowed_seq;/* Seqence no to catch updates */int cpuset_mem_spread_rotor;int cpuset_slab_spread_rotor;#endif#ifdef CONFIG_CGROUPS/* Control Group info protected by css_set_lock */struct css_set __rcu *cgroups;/* cg_list protected by css_set_lock and tsk->alloc_lock */struct list_head cg_list;#endif#ifdef CONFIG_FUTEXstruct robust_list_head __user *robust_list;#ifdef CONFIG_COMPATstruct compat_robust_list_head __user *compat_robust_list;#endifstruct list_head pi_state_list;struct futex_pi_state *pi_state_cache;#endif#ifdef CONFIG_PERF_EVENTSstruct perf_event_context *perf_event_ctxp[perf_nr_task_contexts];struct mutex perf_event_mutex;struct list_head perf_event_list;#endif#ifdef CONFIG_DEBUG_PREEMPTunsigned long preempt_disable_ip;#endif#ifdef CONFIG_NUMAstruct mempolicy *mempolicy;/* Protected by alloc_lock */short il_next;short pref_node_fork;#endif#ifdef CONFIG_NUMA_BALANCINGint numa_scan_seq;unsigned int numa_scan_period;unsigned int numa_scan_period_max;int numa_preferred_nid;unsigned long numa_migrate_retry;u64 node_stamp;/* migration stamp  */u64 last_task_numa_placement;u64 last_sum_exec_runtime;struct callback_head numa_work;struct list_head numa_entry;struct numa_group *numa_group;/* * numa_faults is an array split into four regions: * faults_memory, faults_cpu, faults_memory_buffer, faults_cpu_buffer * in this precise order. * * faults_memory: Exponential decaying average of faults on a per-node * basis. Scheduling placement decisions are made based on these * counts. The values remain static for the duration of a PTE scan. * faults_cpu: Track the nodes the process was running on when a NUMA * hinting fault was incurred. * faults_memory_buffer and faults_cpu_buffer: Record faults per node * during the current scan window. When the scan completes, the counts * in faults_memory and faults_cpu decay and these values are copied. */unsigned long *numa_faults;unsigned long total_numa_faults;/* * numa_faults_locality tracks if faults recorded during the last * scan window were remote/local or failed to migrate. The task scan * period is adapted based on the locality of the faults with different * weights depending on whether they were shared or private faults */unsigned long numa_faults_locality[3];unsigned long numa_pages_migrated;#endif /* CONFIG_NUMA_BALANCING */#ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSHstruct tlbflush_unmap_batch tlb_ubc;#endifstruct rcu_head rcu;/* * cache last used pipe for splice */struct pipe_inode_info *splice_pipe;struct page_frag task_frag;#ifdefCONFIG_TASK_DELAY_ACCTstruct task_delay_info *delays;#endif#ifdef CONFIG_FAULT_INJECTIONint make_it_fail;#endif/* * when (nr_dirtied >= nr_dirtied_pause), it's time to call * balance_dirty_pages() for some dirty throttling pause */int nr_dirtied;int nr_dirtied_pause;unsigned long dirty_paused_when; /* start of a write-and-pause period */#ifdef CONFIG_LATENCYTOPint latency_record_count;struct latency_record latency_record[LT_SAVECOUNT];#endif/* * time slack values; these are used to round up poll() and * select() etc timeout values. These are in nanoseconds. */u64 timer_slack_ns;u64 default_timer_slack_ns;#ifdef CONFIG_KASANunsigned int kasan_depth;#endif#ifdef CONFIG_FUNCTION_GRAPH_TRACER/* Index of current stored address in ret_stack */int curr_ret_stack;/* Stack of return addresses for return function tracing */struct ftrace_ret_stack*ret_stack;/* time stamp for last schedule */unsigned long long ftrace_timestamp;/* * Number of functions that haven't been traced * because of depth overrun. */atomic_t trace_overrun;/* Pause for the tracing */atomic_t tracing_graph_pause;#endif#ifdef CONFIG_TRACING/* state flags for use by tracers */unsigned long trace;/* bitmask and counter of trace recursion */unsigned long trace_recursion;#endif /* CONFIG_TRACING */#ifdef CONFIG_KCOV/* Coverage collection mode enabled for this task (0 if disabled). */enum kcov_mode kcov_mode;/* Size of the kcov_area. */unsignedkcov_size;/* Buffer for coverage collection. */void*kcov_area;/* kcov desciptor wired with this task or NULL. */struct kcov*kcov;#endif#ifdef CONFIG_MEMCGstruct mem_cgroup *memcg_in_oom;gfp_t memcg_oom_gfp_mask;int memcg_oom_order;/* number of pages to reclaim on returning to userland */unsigned int memcg_nr_pages_over_high;#endif#ifdef CONFIG_UPROBESstruct uprobe_task *utask;#endif#if defined(CONFIG_BCACHE) || defined(CONFIG_BCACHE_MODULE)unsigned intsequential_io;unsigned intsequential_io_avg;#endif#ifdef CONFIG_DEBUG_ATOMIC_SLEEPunsigned longtask_state_change;#endifint pagefault_disabled;#ifdef CONFIG_MMUstruct task_struct *oom_reaper_list;#endif#ifdef CONFIG_VMAP_STACKstruct vm_struct *stack_vm_area;#endif#ifdef CONFIG_THREAD_INFO_IN_TASK/* A live task holds one reference. */atomic_t stack_refcount;#endif/* CPU-specific state of this task */struct thread_struct thread;/* * WARNING: on x86, 'thread_struct' contains a variable-sized * structure.  It *MUST* be at the end of 'task_struct'. * * Do not put anything below here! */};

进程描述符当然是在进程创建时候被创建，也就是在fork时候。