3.2.5.2 Prozesskontrollblock unter Linux
Das folgende Videos zeigt, wie man in den Quelltexten des Linux-Kernels die Deklaration des Linux-Prozesskontrollblocks (task_struct) findet, und wie der Zusammenhang mit der Prozesstabelle ist.
video
task_struct: Deklaration des Linux-Prozesskontrollblocks
Der folgende Auszug aus der Quelltext-Datei sched.h des Linux-Kernels (Version 3.13.0) zeigt die Deklaration der Datenstruktur task_struct. Dabei handelt es sich um den Prozesskontrollblock, wie er von Linux verwendet wird.
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 #ifdef CONFIG_SMP
9 struct llist_node wake_entry;
10 int on_cpu;
11 struct task_struct *last_wakee;
12 unsigned long wakee_flips;
13 unsigned long wakee_flip_decay_ts;
14
15 int wake_cpu;
16 #endif
17 int on_rq;
18
19 int prio, static_prio, normal_prio;
20 unsigned int rt_priority;
21 const struct sched_class *sched_class;
22 struct sched_entity se;
23 struct sched_rt_entity rt;
24 #ifdef CONFIG_CGROUP_SCHED
25 struct task_group *sched_task_group;
26 #endif
27
28 #ifdef CONFIG_PREEMPT_NOTIFIERS
29 /* list of struct preempt_notifier: */
30 struct hlist_head preempt_notifiers;
31 #endif
32
33 #ifdef CONFIG_BLK_DEV_IO_TRACE
34 unsigned int btrace_seq;
35 #endif
36
37 unsigned int policy;
38 int nr_cpus_allowed;
39 cpumask_t cpus_allowed;
40
41 #ifdef CONFIG_PREEMPT_RCU
42 int rcu_read_lock_nesting;
43 char rcu_read_unlock_special;
44 struct list_head rcu_node_entry;
45 #endif /* #ifdef CONFIG_PREEMPT_RCU */
46 #ifdef CONFIG_TREE_PREEMPT_RCU
47 struct rcu_node *rcu_blocked_node;
48 #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
49 #ifdef CONFIG_RCU_BOOST
50 struct rt_mutex *rcu_boost_mutex;
51 #endif /* #ifdef CONFIG_RCU_BOOST */
52
53 #if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
54 struct sched_info sched_info;
55 #endif
56
57 struct list_head tasks;
58 #ifdef CONFIG_SMP
59 struct plist_node pushable_tasks;
60 #endif
61
62 struct mm_struct *mm, *active_mm;
63 #ifdef CONFIG_COMPAT_BRK
64 unsigned brk_randomized:1;
65 #endif
66 #if defined(SPLIT_RSS_COUNTING)
67 struct task_rss_stat rss_stat;
68 #endif
69 /* task state */
70 int exit_state;
71 int exit_code, exit_signal;
72 int pdeath_signal; /* The signal sent when the parent dies */
73 unsigned int jobctl; /* JOBCTL_*, siglock protected */
74
75 /* Used for emulating ABI behavior of previous Linux versions */
76 unsigned int personality;
77
78 unsigned did_exec:1;
79 unsigned in_execve:1; /* Tell the LSMs that the process is doing an
80 * execve */
81 unsigned in_iowait:1;
82
83 /* task may not gain privileges */
84 unsigned no_new_privs:1;
85
86 /* Revert to default priority/policy when forking */
87 unsigned sched_reset_on_fork:1;
88 unsigned sched_contributes_to_load:1;
89
90 pid_t pid;
91 pid_t tgid;
92
93 #ifdef CONFIG_CC_STACKPROTECTOR
94 /* Canary value for the -fstack-protector gcc feature */
95 unsigned long stack_canary;
96 #endif
97 /*
98 * pointers to (original) parent process, youngest child, younger sibling,
99 * older sibling, respectively. (p->father can be replaced with
100 * p->real_parent->pid)
101 */
102 struct task_struct __rcu *real_parent; /* real parent process */
103 struct task_struct __rcu *parent; /* recipient of SIGCHLD, wait4() reports */
104 /*
105 * children/sibling forms the list of my natural children
106 */
107 struct list_head children; /* list of my children */
108 struct list_head sibling; /* linkage in my parent's children list */
109 struct task_struct *group_leader; /* threadgroup leader */
110
111 /*
112 * ptraced is the list of tasks this task is using ptrace on.
113 * This includes both natural children and PTRACE_ATTACH targets.
114 * p->ptrace_entry is p's link on the p->parent->ptraced list.
115 */
116 struct list_head ptraced;
117 struct list_head ptrace_entry;
118
119 /* PID/PID hash table linkage. */
120 struct pid_link pids[PIDTYPE_MAX];
121 struct list_head thread_group;
122 struct list_head thread_node;
123
124 struct completion *vfork_done; /* for vfork() */
125 int __user *set_child_tid; /* CLONE_CHILD_SETTID */
126 int __user *clear_child_tid; /* CLONE_CHILD_CLEARTID */
127
128 cputime_t utime, stime, utimescaled, stimescaled;
129 cputime_t gtime;
130 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
131 struct cputime prev_cputime;
132 #endif
133 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
134 seqlock_t vtime_seqlock;
135 unsigned long long vtime_snap;
136 enum {
137 VTIME_SLEEPING = 0,
138 VTIME_USER,
139 VTIME_SYS,
140 } vtime_snap_whence;
141 #endif
142 unsigned long nvcsw, nivcsw; /* context switch counts */
143 struct timespec start_time; /* monotonic time */
144 struct timespec real_start_time; /* boot based time */
145 /* mm fault and swap info: this can arguably be seen as either mm-specific or thread-specific */
146 unsigned long min_flt, maj_flt;
147
148 struct task_cputime cputime_expires;
149 struct list_head cpu_timers[3];
150
151 /* process credentials */
152 const struct cred __rcu *real_cred; /* objective and real subjective task
153 * credentials (COW) */
154 const struct cred __rcu *cred; /* effective (overridable) subjective task
155 * credentials (COW) */
156 char comm[TASK_COMM_LEN]; /* executable name excluding path
157 - access with [gs]et_task_comm (which lock
158 it with task_lock())
159 - initialized normally by setup_new_exec */
160 /* file system info */
161 int link_count, total_link_count;
162 #ifdef CONFIG_SYSVIPC
163 /* ipc stuff */
164 struct sysv_sem sysvsem;
165 #endif
166 #ifdef CONFIG_DETECT_HUNG_TASK
167 /* hung task detection */
168 unsigned long last_switch_count;
169 #endif
170 /* CPU-specific state of this task */
171 struct thread_struct thread;
172 /* filesystem information */
173 struct fs_struct *fs;
174 /* open file information */
175 struct files_struct *files;
176 /* namespaces */
177 struct nsproxy *nsproxy;
178 /* signal handlers */
179 struct signal_struct *signal;
180 struct sighand_struct *sighand;
181
182 sigset_t blocked, real_blocked;
183 sigset_t saved_sigmask; /* restored if set_restore_sigmask() was used */
184 struct sigpending pending;
185
186 unsigned long sas_ss_sp;
187 size_t sas_ss_size;
188 int (*notifier)(void *priv);
189 void *notifier_data;
190 sigset_t *notifier_mask;
191 struct callback_head *task_works;
192
193 struct audit_context *audit_context;
194 #ifdef CONFIG_AUDITSYSCALL
195 kuid_t loginuid;
196 unsigned int sessionid;
197 #endif
198 struct seccomp seccomp;
199
200 /* Thread group tracking */
201 u32 parent_exec_id;
202 u32 self_exec_id;
203 /* Protection of (de-)allocation: mm, files, fs, tty, keyrings, mems_allowed,
204 * mempolicy */
205 spinlock_t alloc_lock;
206
207 /* Protection of the PI data structures: */
208 raw_spinlock_t pi_lock;
209
210 #ifdef CONFIG_RT_MUTEXES
211 /* PI waiters blocked on a rt_mutex held by this task */
212 struct plist_head pi_waiters;
213 /* Deadlock detection and priority inheritance handling */
214 struct rt_mutex_waiter *pi_blocked_on;
215 #endif
216
217 #ifdef CONFIG_DEBUG_MUTEXES
218 /* mutex deadlock detection */
219 struct mutex_waiter *blocked_on;
220 #endif
221 #ifdef CONFIG_TRACE_IRQFLAGS
222 unsigned int irq_events;
223 unsigned long hardirq_enable_ip;
224 unsigned long hardirq_disable_ip;
225 unsigned int hardirq_enable_event;
226 unsigned int hardirq_disable_event;
227 int hardirqs_enabled;
228 int hardirq_context;
229 unsigned long softirq_disable_ip;
230 unsigned long softirq_enable_ip;
231 unsigned int softirq_disable_event;
232 unsigned int softirq_enable_event;
233 int softirqs_enabled;
234 int softirq_context;
235 #endif
236 #ifdef CONFIG_LOCKDEP
237 # define MAX_LOCK_DEPTH 48UL
238 u64 curr_chain_key;
239 int lockdep_depth;
240 unsigned int lockdep_recursion;
241 struct held_lock held_locks[MAX_LOCK_DEPTH];
242 gfp_t lockdep_reclaim_gfp;
243 #endif
244
245 /* journalling filesystem info */
246 void *journal_info;
247
248 /* stacked block device info */
249 struct bio_list *bio_list;
250
251 #ifdef CONFIG_BLOCK
252 /* stack plugging */
253 struct blk_plug *plug;
254 #endif
255
256 /* VM state */
257 struct reclaim_state *reclaim_state;
258
259 struct backing_dev_info *backing_dev_info;
260
261 struct io_context *io_context;
262
263 unsigned long ptrace_message;
264 siginfo_t *last_siginfo; /* For ptrace use. */
265 struct task_io_accounting ioac;
266 #if defined(CONFIG_TASK_XACCT)
267 u64 acct_rss_mem1; /* accumulated rss usage */
268 u64 acct_vm_mem1; /* accumulated virtual memory usage */
269 cputime_t acct_timexpd; /* stime + utime since last update */
270 #endif
271 #ifdef CONFIG_CPUSETS
272 nodemask_t mems_allowed; /* Protected by alloc_lock */
273 seqcount_t mems_allowed_seq; /* Seqence no to catch updates */
274 int cpuset_mem_spread_rotor;
275 int cpuset_slab_spread_rotor;
276 #endif
277 #ifdef CONFIG_CGROUPS
278 /* Control Group info protected by css_set_lock */
279 struct css_set __rcu *cgroups;
280 /* cg_list protected by css_set_lock and tsk->alloc_lock */
281 struct list_head cg_list;
282 #endif
283 #ifdef CONFIG_FUTEX
284 struct robust_list_head __user *robust_list;
285 #ifdef CONFIG_COMPAT
286 struct compat_robust_list_head __user *compat_robust_list;
287 #endif
288 struct list_head pi_state_list;
289 struct futex_pi_state *pi_state_cache;
290 #endif
291 #ifdef CONFIG_PERF_EVENTS
292 struct perf_event_context *perf_event_ctxp[perf_nr_task_contexts];
293 struct mutex perf_event_mutex;
294 struct list_head perf_event_list;
295 #endif
296 #ifdef CONFIG_NUMA
297 struct mempolicy *mempolicy; /* Protected by alloc_lock */
298 short il_next;
299 short pref_node_fork;
300 #endif
301 #ifdef CONFIG_NUMA_BALANCING
302 int numa_scan_seq;
303 unsigned int numa_scan_period;
304 unsigned int numa_scan_period_max;
305 int numa_preferred_nid;
306 int numa_migrate_deferred;
307 unsigned long numa_migrate_retry;
308 u64 node_stamp; /* migration stamp */
309 struct callback_head numa_work;
310
311 struct list_head numa_entry;
312 struct numa_group *numa_group;
313
314 /*
315 * Exponential decaying average of faults on a per-node basis.
316 * Scheduling placement decisions are made based on the these counts.
317 * The values remain static for the duration of a PTE scan
318 */
319 unsigned long *numa_faults;
320 unsigned long total_numa_faults;
321
322 /*
323 * numa_faults_buffer records faults per node during the current
324 * scan window. When the scan completes, the counts in numa_faults
325 * decay and these values are copied.
326 */
327 unsigned long *numa_faults_buffer;
328
329 /*
330 * numa_faults_locality tracks if faults recorded during the last
331 * scan window were remote/local. The task scan period is adapted
332 * based on the locality of the faults with different weights
333 * depending on whether they were shared or private faults
334 */
335 unsigned long numa_faults_locality[2];
336
337 unsigned long numa_pages_migrated;
338 #endif /* CONFIG_NUMA_BALANCING */
339
340 struct rcu_head rcu;
341
342 /*
343 * cache last used pipe for splice
344 */
345 struct pipe_inode_info *splice_pipe;
346
347 struct page_frag task_frag;
348
349 #ifdef CONFIG_TASK_DELAY_ACCT
350 struct task_delay_info *delays;
351 #endif
352 #ifdef CONFIG_FAULT_INJECTION
353 int make_it_fail;
354 #endif
355 /*
356 * when (nr_dirtied >= nr_dirtied_pause), it's time to call
357 * balance_dirty_pages() for some dirty throttling pause
358 */
359 int nr_dirtied;
360 int nr_dirtied_pause;
361 unsigned long dirty_paused_when; /* start of a write-and-pause period */
362
363 #ifdef CONFIG_LATENCYTOP
364 int latency_record_count;
365 struct latency_record latency_record[LT_SAVECOUNT];
366 #endif
367 /*
368 * time slack values; these are used to round up poll() and
369 * select() etc timeout values. These are in nanoseconds.
370 */
371 unsigned long timer_slack_ns;
372 unsigned long default_timer_slack_ns;
373
374 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
375 /* Index of current stored address in ret_stack */
376 int curr_ret_stack;
377 /* Stack of return addresses for return function tracing */
378 struct ftrace_ret_stack *ret_stack;
379 /* time stamp for last schedule */
380 unsigned long long ftrace_timestamp;
381 /*
382 * Number of functions that haven't been traced
383 * because of depth overrun.
384 */
385 atomic_t trace_overrun;
386 /* Pause for the tracing */
387 atomic_t tracing_graph_pause;
388 #endif
389 #ifdef CONFIG_TRACING
390 /* state flags for use by tracers */
391 unsigned long trace;
392 /* bitmask and counter of trace recursion */
393 unsigned long trace_recursion;
394 #endif /* CONFIG_TRACING */
395 #ifdef CONFIG_MEMCG /* memcg uses this to do batch job */
396 struct memcg_batch_info {
397 int do_batch; /* incremented when batch uncharge started */
398 struct mem_cgroup *memcg; /* target memcg of uncharge */
399 unsigned long nr_pages; /* uncharged usage */
400 unsigned long memsw_nr_pages; /* uncharged mem+swap usage */
401 } memcg_batch;
402 unsigned int memcg_kmem_skip_account;
403 struct memcg_oom_info {
404 struct mem_cgroup *memcg;
405 gfp_t gfp_mask;
406 int order;
407 unsigned int may_oom:1;
408 } memcg_oom;
409 #endif
410 #ifdef CONFIG_UPROBES
411 struct uprobe_task *utask;
412 #endif
413 #if defined(CONFIG_BCACHE) || defined(CONFIG_BCACHE_MODULE)
414 unsigned int sequential_io;
415 unsigned int sequential_io_avg;
416 #endif
417 };
Das folgende Bild wurde im Video erläutert:
Aufgabe 1
Aufgabe
Im Video wurde der Zusammenhang zwischen der Datenstruktur task_struct und den Spalten der Prozesstabelle erläutert.
Was schätzt du:
Aus wievielen Spalten besteht in etwa die Prozesstabelle?
- Aus 5 bis 10 Spalten.
- Aus 25 bis 30 Spalten.
- Aus mehr als 50 Spalten.
Beispiel: Prozesskontrollblock unter Linux
Hinweis
Weiterführende Literatur
Achilles 2006 zeigt in Kapitel 3.1 den Linux Process Control Block. Die Lektüre dieser Quelle sei ausdrücklich empfohlen.
Studierende sind oftmals berechtigt, eine PDF-Version dieses Buches ohne entstehende Kosten über ihre Hochschulen von Springerlink zu beziehen.
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