task_struct structure

3.2. Process Descriptor

Figure 3-1. The Linux process descriptor

/*include/linux/sched.h,linux2.6.32.2*/struct task_struct {volatile long state;/* -1 unrunnable, 0 runnable, >0 stopped */void *stack;atomic_t usage;unsigned int flags;/* per process flags, defined below */unsigned int ptrace;int lock_depth;/* BKL lock depth */#ifdef CONFIG_SMP#ifdef __ARCH_WANT_UNLOCKED_CTXSWint oncpu;#endif#endifint 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_PREEMPT_NOTIFIERS/* list of struct preempt_notifier: */struct hlist_head preempt_notifiers;#endif/* * fpu_counter contains the number of consecutive context switches * that the FPU is used. If this is over a threshold, the lazy fpu * saving becomes unlazy to save the trap. This is an unsigned char * so that after 256 times the counter wraps and the behavior turns * lazy again; this to deal with bursty apps that only use FPU for * a short time */unsigned char fpu_counter;#ifdef CONFIG_BLK_DEV_IO_TRACEunsigned int btrace_seq;#endifunsigned int policy;cpumask_t cpus_allowed;int rcu_read_lock_nesting;#ifdef CONFIG_TREE_PREEMPT_RCUchar rcu_read_unlock_special;struct rcu_node *rcu_blocked_node;struct list_head rcu_node_entry;#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)struct sched_info sched_info;#endifstruct list_head tasks;struct plist_node pushable_tasks;struct mm_struct *mm, *active_mm;/* task state */int exit_state;int exit_code, exit_signal;int pdeath_signal;  /*  The signal sent when the parent dies  *//* ??? */unsigned int personality;unsigned did_exec:1;unsigned in_execve:1;/* Tell the LSMs that the process is doing an * execve */unsigned in_iowait:1;/* Revert to default priority/policy when forking */unsigned sched_reset_on_fork:1;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 *real_parent; /* real parent process */struct task_struct *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;/* * This is the tracer handle for the ptrace BTS extension. * This field actually belongs to the ptracer task. */struct bts_context *bts;/* PID/PID hash table linkage. */struct pid_link pids[PIDTYPE_MAX];struct list_head thread_group;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;cputime_t prev_utime, prev_stime;unsigned long nvcsw, nivcsw; /* context switch counts */struct timespec start_time; /* monotonic time */struct timespec real_start_time;/* boot based time *//* 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 *real_cred;/* objective and real subjective task * credentials (COW) */const struct cred *cred;/* effective (overridable) subjective task * credentials (COW) */struct mutex cred_guard_mutex;/* guard against foreign influences on * credential calculations * (notably. ptrace) */struct cred *replacement_session_keyring; /* for KEYCTL_SESSION_TO_PARENT */char comm[TASK_COMM_LEN]; /* executable name excluding path     - access with [gs]et_task_comm (which lock       it with task_lock())     - initialized normally by flush_old_exec *//* file system info */int link_count, total_link_count;#ifdef CONFIG_SYSVIPC/* ipc stuff */struct sysv_sem sysvsem;#endif#ifdef CONFIG_DETECT_HUNG_TASK/* hung task detection */unsigned long last_switch_count;#endif/* CPU-specific state of this task */struct thread_struct thread;/* 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;int (*notifier)(void *priv);void *notifier_data;sigset_t *notifier_mask;struct audit_context *audit_context;#ifdef CONFIG_AUDITSYSCALLuid_t loginuid;unsigned int sessionid;#endifseccomp_t 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;#ifdef CONFIG_GENERIC_HARDIRQS/* IRQ handler threads */struct irqaction *irqaction;#endif/* Protection of the PI data structures: */spinlock_t pi_lock;#ifdef CONFIG_RT_MUTEXES/* PI waiters blocked on a rt_mutex held by this task */struct plist_head pi_waiters;/* 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;int hardirqs_enabled;unsigned long hardirq_enable_ip;unsigned int hardirq_enable_event;unsigned long hardirq_disable_ip;unsigned int hardirq_disable_event;int softirqs_enabled;unsigned long softirq_disable_ip;unsigned int softirq_disable_event;unsigned long softirq_enable_ip;unsigned int softirq_enable_event;int hardirq_context;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/* journalling filesystem info */void *journal_info;/* stacked block device info */struct bio *bio_list, **bio_tail;/* 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 */int cpuset_mem_spread_rotor;#endif#ifdef CONFIG_CGROUPS/* Control Group info protected by css_set_lock */struct css_set *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;struct mutex perf_event_mutex;struct list_head perf_event_list;#endif#ifdef CONFIG_NUMAstruct mempolicy *mempolicy;/* Protected by alloc_lock */short il_next;#endifatomic_t fs_excl;/* holding fs exclusive resources */struct rcu_head rcu;/* * cache last used pipe for splice */struct pipe_inode_info *splice_pipe;#ifdefCONFIG_TASK_DELAY_ACCTstruct task_delay_info *delays;#endif#ifdef CONFIG_FAULT_INJECTIONint make_it_fail;#endifstruct prop_local_single dirties;#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. */unsigned long timer_slack_ns;unsigned long default_timer_slack_ns;struct list_head*scm_work_list;#ifdef CONFIG_FUNCTION_GRAPH_TRACER/* Index of current stored adress 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 of trace recursion */unsigned long trace_recursion;#endif /* CONFIG_TRACING */unsigned long stack_start;};