Linux 源码阅读 进程管理
版本：2.6.24
1.准备知识
1.1 Linux系统中，进程是最小的调度单位；
1.2 PCB数据结构：task_struct （Location：linux-2.6.24\include\linux\sched.h）
1 struct task_struct { 2 volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */ 3 void *stack; 4 atomic_t usage; 5 unsigned int flags; /* per process flags, defined below */ 6 unsigned int ptrace; 7 8 int lock_depth; /* BKL lock depth */ 9 10 #ifdef CONFIG_SMP 11 #ifdef __ARCH_WANT_UNLOCKED_CTXSW 12 int oncpu; 13 #endif 14 #endif 15 16 int prio, static_prio, normal_prio; 17 struct list_head run_list; 18 const struct sched_class *sched_class; 19 struct sched_entity se; 20 21 #ifdef CONFIG_PREEMPT_NOTIFIERS 22 /* list of struct preempt_notifier: */ 23 struct hlist_head preempt_notifiers; 24 #endif 25 26 unsigned short ioprio; 27 /* 28 * fpu_counter contains the number of consecutive context switches 29 * that the FPU is used. If this is over a threshold, the lazy fpu 30 * saving becomes unlazy to save the trap. This is an unsigned char 31 * so that after 256 times the counter wraps and the behavior turns 32 * lazy again; this to deal with bursty apps that only use FPU for 33 * a short time 34 */ 35 unsigned char fpu_counter; 36 s8 oomkilladj; /* OOM kill score adjustment (bit shift). */ 37 #ifdef CONFIG_BLK_DEV_IO_TRACE 38 unsigned int btrace_seq; 39 #endif 40 41 unsigned int policy; 42 cpumask_t cpus_allowed; 43 unsigned int time_slice; 44 45 #if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT) 46 struct sched_info sched_info; 47 #endif 48 49 struct list_head tasks; 50 /* 51 * ptrace_list/ptrace_children forms the list of my children 52 * that were stolen by a ptracer. 53 */ 54 struct list_head ptrace_children; 55 struct list_head ptrace_list; 56 57 struct mm_struct *mm, *active_mm; 58 59 /* task state */ 60 struct linux_binfmt *binfmt; 61 int exit_state; 62 int exit_code, exit_signal; 63 int pdeath_signal; /* The signal sent when the parent dies */ 64 /* ??? */ 65 unsigned int personality; 66 unsigned did_exec:1; 67 pid_t pid; 68 pid_t tgid; 69 70 #ifdef CONFIG_CC_STACKPROTECTOR 71 /* Canary value for the -fstack-protector gcc feature */ 72 unsigned long stack_canary; 73 #endif 74 /* 75 * pointers to (original) parent process, youngest child, younger sibling, 76 * older sibling, respectively. (p->father can be replaced with 77 * p->parent->pid) 78 */ 79 struct task_struct *real_parent; /* real parent process (when being debugged) */ 80 struct task_struct *parent; /* parent process */ 81 /* 82 * children/sibling forms the list of my children plus the 83 * tasks I'm ptracing. 84 */ 85 struct list_head children; /* list of my children */ 86 struct list_head sibling; /* linkage in my parent's children list */ 87 struct task_struct *group_leader; /* threadgroup leader */ 88 89 /* PID/PID hash table linkage. */ 90 struct pid_link pids[PIDTYPE_MAX]; 91 struct list_head thread_group; 92 93 struct completion *vfork_done; /* for vfork() */ 94 int __user *set_child_tid; /* CLONE_CHILD_SETTID */ 95 int __user *clear_child_tid; /* CLONE_CHILD_CLEARTID */ 96 97 unsigned int rt_priority; 98 cputime_t utime, stime, utimescaled, stimescaled; 99 cputime_t gtime; 100 cputime_t prev_utime, prev_stime; 101 unsigned long nvcsw, nivcsw; /* context switch counts */ 102 struct timespec start_time; /* monotonic time */ 103 struct timespec real_start_time; /* boot based time */ 104 /* mm fault and swap info: this can arguably be seen as either mm-specific or thread-specific */ 105 unsigned long min_flt, maj_flt; 106 107 cputime_t it_prof_expires, it_virt_expires; 108 unsigned long long it_sched_expires; 109 struct list_head cpu_timers[3]; 110 111 /* process credentials */ 112 uid_t uid,euid,suid,fsuid; 113 gid_t gid,egid,sgid,fsgid; 114 struct group_info *group_info; 115 kernel_cap_t cap_effective, cap_inheritable, cap_permitted; 116 unsigned keep_capabilities:1; 117 struct user_struct *user; 118 #ifdef CONFIG_KEYS 119 struct key *request_key_auth; /* assumed request_key authority */ 120 struct key *thread_keyring; /* keyring private to this thread */ 121 unsigned char jit_keyring; /* default keyring to attach requested keys to */ 122 #endif 123 char comm[TASK_COMM_LEN]; /* executable name excluding path 124 - access with [gs]et_task_comm (which lock 125 it with task_lock()) 126 - initialized normally by flush_old_exec */ 127 /* file system info */ 128 int link_count, total_link_count; 129 #ifdef CONFIG_SYSVIPC 130 /* ipc stuff */ 131 struct sysv_sem sysvsem; 132 #endif 133 /* CPU-specific state of this task */ 134 struct thread_struct thread; 135 /* filesystem information */ 136 struct fs_struct *fs; 137 /* open file information */ 138 struct files_struct *files; 139 /* namespaces */ 140 struct nsproxy *nsproxy; 141 /* signal handlers */ 142 struct signal_struct *signal; 143 struct sighand_struct *sighand; 144 145 sigset_t blocked, real_blocked; 146 sigset_t saved_sigmask; /* To be restored with TIF_RESTORE_SIGMASK */ 147 struct sigpending pending; 148 149 unsigned long sas_ss_sp; 150 size_t sas_ss_size; 151 int (*notifier)(void *priv); 152 void *notifier_data; 153 sigset_t *notifier_mask; 154 #ifdef CONFIG_SECURITY 155 void *security; 156 #endif 157 struct audit_context *audit_context; 158 seccomp_t seccomp; 159 160 /* Thread group tracking */ 161 u32 parent_exec_id; 162 u32 self_exec_id; 163 /* Protection of (de-)allocation: mm, files, fs, tty, keyrings */ 164 spinlock_t alloc_lock; 165 166 /* Protection of the PI data structures: */ 167 spinlock_t pi_lock; 168 169 #ifdef CONFIG_RT_MUTEXES 170 /* PI waiters blocked on a rt_mutex held by this task */ 171 struct plist_head pi_waiters; 172 /* Deadlock detection and priority inheritance handling */ 173 struct rt_mutex_waiter *pi_blocked_on; 174 #endif 175 176 #ifdef CONFIG_DEBUG_MUTEXES 177 /* mutex deadlock detection */ 178 struct mutex_waiter *blocked_on; 179 #endif 180 #ifdef CONFIG_TRACE_IRQFLAGS 181 unsigned int irq_events; 182 int hardirqs_enabled; 183 unsigned long hardirq_enable_ip; 184 unsigned int hardirq_enable_event; 185 unsigned long hardirq_disable_ip; 186 unsigned int hardirq_disable_event; 187 int softirqs_enabled; 188 unsigned long softirq_disable_ip; 189 unsigned int softirq_disable_event; 190 unsigned long softirq_enable_ip; 191 unsigned int softirq_enable_event; 192 int hardirq_context; 193 int softirq_context; 194 #endif 195 #ifdef CONFIG_LOCKDEP 196 # define MAX_LOCK_DEPTH 30UL 197 u64 curr_chain_key; 198 int lockdep_depth; 199 struct held_lock held_locks[MAX_LOCK_DEPTH]; 200 unsigned int lockdep_recursion; 201 #endif 202 203 /* journalling filesystem info */ 204 void *journal_info; 205 206 /* stacked block device info */ 207 struct bio *bio_list, **bio_tail; 208 209 /* VM state */ 210 struct reclaim_state *reclaim_state; 211 212 struct backing_dev_info *backing_dev_info; 213 214 struct io_context *io_context; 215 216 unsigned long ptrace_message; 217 siginfo_t *last_siginfo; /* For ptrace use. */ 218 #ifdef CONFIG_TASK_XACCT 219 /* i/o counters(bytes read/written, #syscalls */ 220 u64 rchar, wchar, syscr, syscw; 221 #endif 222 struct task_io_accounting ioac; 223 #if defined(CONFIG_TASK_XACCT) 224 u64 acct_rss_mem1; /* accumulated rss usage */ 225 u64 acct_vm_mem1; /* accumulated virtual memory usage */ 226 cputime_t acct_stimexpd;/* stime since last update */ 227 #endif 228 #ifdef CONFIG_NUMA 229 struct mempolicy *mempolicy; 230 short il_next; 231 #endif 232 #ifdef CONFIG_CPUSETS 233 nodemask_t mems_allowed; 234 int cpuset_mems_generation; 235 int cpuset_mem_spread_rotor; 236 #endif 237 #ifdef CONFIG_CGROUPS 238 /* Control Group info protected by css_set_lock */ 239 struct css_set *cgroups; 240 /* cg_list protected by css_set_lock and tsk->alloc_lock */ 241 struct list_head cg_list; 242 #endif 243 #ifdef CONFIG_FUTEX 244 struct robust_list_head __user *robust_list; 245 #ifdef CONFIG_COMPAT 246 struct compat_robust_list_head __user *compat_robust_list; 247 #endif 248 struct list_head pi_state_list; 249 struct futex_pi_state *pi_state_cache; 250 #endif 251 atomic_t fs_excl; /* holding fs exclusive resources */ 252 struct rcu_head rcu; 253 254 /* 255 * cache last used pipe for splice 256 */ 257 struct pipe_inode_info *splice_pipe; 258 #ifdef CONFIG_TASK_DELAY_ACCT 259 struct task_delay_info *delays; 260 #endif 261 #ifdef CONFIG_FAULT_INJECTION 262 int make_it_fail; 263 #endif 264 struct prop_local_single dirties; 265 };