xref: /linux/include/linux/sched/signal.h (revision da51bbcdbace8f43adf6066934c3926b656376e5)
1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_SCHED_SIGNAL_H
3 #define _LINUX_SCHED_SIGNAL_H
4 
5 #include <linux/rculist.h>
6 #include <linux/signal.h>
7 #include <linux/sched.h>
8 #include <linux/sched/jobctl.h>
9 #include <linux/sched/task.h>
10 #include <linux/cred.h>
11 #include <linux/refcount.h>
12 #include <linux/pid.h>
13 #include <linux/posix-timers.h>
14 #include <linux/mm_types.h>
15 #include <asm/ptrace.h>
16 
17 /*
18  * Types defining task->signal and task->sighand and APIs using them:
19  */
20 
21 struct sighand_struct {
22 	spinlock_t		siglock;
23 	refcount_t		count;
24 	wait_queue_head_t	signalfd_wqh;
25 	struct k_sigaction	action[_NSIG];
26 };
27 
28 /*
29  * Per-process accounting stats:
30  */
31 struct pacct_struct {
32 	int			ac_flag;
33 	long			ac_exitcode;
34 	unsigned long		ac_mem;
35 	u64			ac_utime, ac_stime;
36 	unsigned long		ac_minflt, ac_majflt;
37 };
38 
39 struct cpu_itimer {
40 	u64 expires;
41 	u64 incr;
42 };
43 
44 /*
45  * This is the atomic variant of task_cputime, which can be used for
46  * storing and updating task_cputime statistics without locking.
47  */
48 struct task_cputime_atomic {
49 	atomic64_t utime;
50 	atomic64_t stime;
51 	atomic64_t sum_exec_runtime;
52 };
53 
54 #define INIT_CPUTIME_ATOMIC \
55 	(struct task_cputime_atomic) {				\
56 		.utime = ATOMIC64_INIT(0),			\
57 		.stime = ATOMIC64_INIT(0),			\
58 		.sum_exec_runtime = ATOMIC64_INIT(0),		\
59 	}
60 /**
61  * struct thread_group_cputimer - thread group interval timer counts
62  * @cputime_atomic:	atomic thread group interval timers.
63  *
64  * This structure contains the version of task_cputime, above, that is
65  * used for thread group CPU timer calculations.
66  */
67 struct thread_group_cputimer {
68 	struct task_cputime_atomic cputime_atomic;
69 };
70 
71 struct multiprocess_signals {
72 	sigset_t signal;
73 	struct hlist_node node;
74 };
75 
76 struct core_thread {
77 	struct task_struct *task;
78 	struct core_thread *next;
79 };
80 
81 struct core_state {
82 	atomic_t nr_threads;
83 	struct core_thread dumper;
84 	struct completion startup;
85 };
86 
87 /*
88  * NOTE! "signal_struct" does not have its own
89  * locking, because a shared signal_struct always
90  * implies a shared sighand_struct, so locking
91  * sighand_struct is always a proper superset of
92  * the locking of signal_struct.
93  */
94 struct signal_struct {
95 	refcount_t		sigcnt;
96 	atomic_t		live;
97 	int			nr_threads;
98 	int			quick_threads;
99 	struct list_head	thread_head;
100 
101 	wait_queue_head_t	wait_chldexit;	/* for wait4() */
102 
103 	/* current thread group signal load-balancing target: */
104 	struct task_struct	*curr_target;
105 
106 	/* shared signal handling: */
107 	struct sigpending	shared_pending;
108 
109 	/* For collecting multiprocess signals during fork */
110 	struct hlist_head	multiprocess;
111 
112 	/* thread group exit support */
113 	int			group_exit_code;
114 	/* notify group_exec_task when notify_count is less or equal to 0 */
115 	int			notify_count;
116 	struct task_struct	*group_exec_task;
117 
118 	/* thread group stop support, overloads group_exit_code too */
119 	int			group_stop_count;
120 	unsigned int		flags; /* see SIGNAL_* flags below */
121 
122 	struct core_state *core_state; /* coredumping support */
123 
124 	/*
125 	 * PR_SET_CHILD_SUBREAPER marks a process, like a service
126 	 * manager, to re-parent orphan (double-forking) child processes
127 	 * to this process instead of 'init'. The service manager is
128 	 * able to receive SIGCHLD signals and is able to investigate
129 	 * the process until it calls wait(). All children of this
130 	 * process will inherit a flag if they should look for a
131 	 * child_subreaper process at exit.
132 	 */
133 	unsigned int		is_child_subreaper:1;
134 	unsigned int		has_child_subreaper:1;
135 
136 #ifdef CONFIG_POSIX_TIMERS
137 
138 	/* POSIX.1b Interval Timers */
139 	unsigned int		next_posix_timer_id;
140 	struct list_head	posix_timers;
141 
142 	/* ITIMER_REAL timer for the process */
143 	struct hrtimer real_timer;
144 	ktime_t it_real_incr;
145 
146 	/*
147 	 * ITIMER_PROF and ITIMER_VIRTUAL timers for the process, we use
148 	 * CPUCLOCK_PROF and CPUCLOCK_VIRT for indexing array as these
149 	 * values are defined to 0 and 1 respectively
150 	 */
151 	struct cpu_itimer it[2];
152 
153 	/*
154 	 * Thread group totals for process CPU timers.
155 	 * See thread_group_cputimer(), et al, for details.
156 	 */
157 	struct thread_group_cputimer cputimer;
158 
159 #endif
160 	/* Empty if CONFIG_POSIX_TIMERS=n */
161 	struct posix_cputimers posix_cputimers;
162 
163 	/* PID/PID hash table linkage. */
164 	struct pid *pids[PIDTYPE_MAX];
165 
166 #ifdef CONFIG_NO_HZ_FULL
167 	atomic_t tick_dep_mask;
168 #endif
169 
170 	struct pid *tty_old_pgrp;
171 
172 	/* boolean value for session group leader */
173 	int leader;
174 
175 	struct tty_struct *tty; /* NULL if no tty */
176 
177 #ifdef CONFIG_SCHED_AUTOGROUP
178 	struct autogroup *autogroup;
179 #endif
180 	/*
181 	 * Cumulative resource counters for dead threads in the group,
182 	 * and for reaped dead child processes forked by this group.
183 	 * Live threads maintain their own counters and add to these
184 	 * in __exit_signal, except for the group leader.
185 	 */
186 	seqlock_t stats_lock;
187 	u64 utime, stime, cutime, cstime;
188 	u64 gtime;
189 	u64 cgtime;
190 	struct prev_cputime prev_cputime;
191 	unsigned long nvcsw, nivcsw, cnvcsw, cnivcsw;
192 	unsigned long min_flt, maj_flt, cmin_flt, cmaj_flt;
193 	unsigned long inblock, oublock, cinblock, coublock;
194 	unsigned long maxrss, cmaxrss;
195 	struct task_io_accounting ioac;
196 
197 	/*
198 	 * Cumulative ns of schedule CPU time fo dead threads in the
199 	 * group, not including a zombie group leader, (This only differs
200 	 * from jiffies_to_ns(utime + stime) if sched_clock uses something
201 	 * other than jiffies.)
202 	 */
203 	unsigned long long sum_sched_runtime;
204 
205 	/*
206 	 * We don't bother to synchronize most readers of this at all,
207 	 * because there is no reader checking a limit that actually needs
208 	 * to get both rlim_cur and rlim_max atomically, and either one
209 	 * alone is a single word that can safely be read normally.
210 	 * getrlimit/setrlimit use task_lock(current->group_leader) to
211 	 * protect this instead of the siglock, because they really
212 	 * have no need to disable irqs.
213 	 */
214 	struct rlimit rlim[RLIM_NLIMITS];
215 
216 #ifdef CONFIG_BSD_PROCESS_ACCT
217 	struct pacct_struct pacct;	/* per-process accounting information */
218 #endif
219 #ifdef CONFIG_TASKSTATS
220 	struct taskstats *stats;
221 #endif
222 #ifdef CONFIG_AUDIT
223 	unsigned audit_tty;
224 	struct tty_audit_buf *tty_audit_buf;
225 #endif
226 
227 	/*
228 	 * Thread is the potential origin of an oom condition; kill first on
229 	 * oom
230 	 */
231 	bool oom_flag_origin;
232 	short oom_score_adj;		/* OOM kill score adjustment */
233 	short oom_score_adj_min;	/* OOM kill score adjustment min value.
234 					 * Only settable by CAP_SYS_RESOURCE. */
235 	struct mm_struct *oom_mm;	/* recorded mm when the thread group got
236 					 * killed by the oom killer */
237 
238 	struct mutex cred_guard_mutex;	/* guard against foreign influences on
239 					 * credential calculations
240 					 * (notably. ptrace)
241 					 * Deprecated do not use in new code.
242 					 * Use exec_update_lock instead.
243 					 */
244 	struct rw_semaphore exec_update_lock;	/* Held while task_struct is
245 						 * being updated during exec,
246 						 * and may have inconsistent
247 						 * permissions.
248 						 */
249 } __randomize_layout;
250 
251 /*
252  * Bits in flags field of signal_struct.
253  */
254 #define SIGNAL_STOP_STOPPED	0x00000001 /* job control stop in effect */
255 #define SIGNAL_STOP_CONTINUED	0x00000002 /* SIGCONT since WCONTINUED reap */
256 #define SIGNAL_GROUP_EXIT	0x00000004 /* group exit in progress */
257 /*
258  * Pending notifications to parent.
259  */
260 #define SIGNAL_CLD_STOPPED	0x00000010
261 #define SIGNAL_CLD_CONTINUED	0x00000020
262 #define SIGNAL_CLD_MASK		(SIGNAL_CLD_STOPPED|SIGNAL_CLD_CONTINUED)
263 
264 #define SIGNAL_UNKILLABLE	0x00000040 /* for init: ignore fatal signals */
265 
266 #define SIGNAL_STOP_MASK (SIGNAL_CLD_MASK | SIGNAL_STOP_STOPPED | \
267 			  SIGNAL_STOP_CONTINUED)
268 
269 static inline void signal_set_stop_flags(struct signal_struct *sig,
270 					 unsigned int flags)
271 {
272 	WARN_ON(sig->flags & SIGNAL_GROUP_EXIT);
273 	sig->flags = (sig->flags & ~SIGNAL_STOP_MASK) | flags;
274 }
275 
276 extern void flush_signals(struct task_struct *);
277 extern void ignore_signals(struct task_struct *);
278 extern void flush_signal_handlers(struct task_struct *, int force_default);
279 extern int dequeue_signal(struct task_struct *task, sigset_t *mask,
280 			  kernel_siginfo_t *info, enum pid_type *type);
281 
282 static inline int kernel_dequeue_signal(void)
283 {
284 	struct task_struct *task = current;
285 	kernel_siginfo_t __info;
286 	enum pid_type __type;
287 	int ret;
288 
289 	spin_lock_irq(&task->sighand->siglock);
290 	ret = dequeue_signal(task, &task->blocked, &__info, &__type);
291 	spin_unlock_irq(&task->sighand->siglock);
292 
293 	return ret;
294 }
295 
296 static inline void kernel_signal_stop(void)
297 {
298 	spin_lock_irq(&current->sighand->siglock);
299 	if (current->jobctl & JOBCTL_STOP_DEQUEUED) {
300 		current->jobctl |= JOBCTL_STOPPED;
301 		set_special_state(TASK_STOPPED);
302 	}
303 	spin_unlock_irq(&current->sighand->siglock);
304 
305 	schedule();
306 }
307 
308 int force_sig_fault_to_task(int sig, int code, void __user *addr,
309 			    struct task_struct *t);
310 int force_sig_fault(int sig, int code, void __user *addr);
311 int send_sig_fault(int sig, int code, void __user *addr, struct task_struct *t);
312 
313 int force_sig_mceerr(int code, void __user *, short);
314 int send_sig_mceerr(int code, void __user *, short, struct task_struct *);
315 
316 int force_sig_bnderr(void __user *addr, void __user *lower, void __user *upper);
317 int force_sig_pkuerr(void __user *addr, u32 pkey);
318 int send_sig_perf(void __user *addr, u32 type, u64 sig_data);
319 
320 int force_sig_ptrace_errno_trap(int errno, void __user *addr);
321 int force_sig_fault_trapno(int sig, int code, void __user *addr, int trapno);
322 int send_sig_fault_trapno(int sig, int code, void __user *addr, int trapno,
323 			struct task_struct *t);
324 int force_sig_seccomp(int syscall, int reason, bool force_coredump);
325 
326 extern int send_sig_info(int, struct kernel_siginfo *, struct task_struct *);
327 extern void force_sigsegv(int sig);
328 extern int force_sig_info(struct kernel_siginfo *);
329 extern int __kill_pgrp_info(int sig, struct kernel_siginfo *info, struct pid *pgrp);
330 extern int kill_pid_info(int sig, struct kernel_siginfo *info, struct pid *pid);
331 extern int kill_pid_usb_asyncio(int sig, int errno, sigval_t addr, struct pid *,
332 				const struct cred *);
333 extern int kill_pgrp(struct pid *pid, int sig, int priv);
334 extern int kill_pid(struct pid *pid, int sig, int priv);
335 extern __must_check bool do_notify_parent(struct task_struct *, int);
336 extern void __wake_up_parent(struct task_struct *p, struct task_struct *parent);
337 extern void force_sig(int);
338 extern void force_fatal_sig(int);
339 extern void force_exit_sig(int);
340 extern int send_sig(int, struct task_struct *, int);
341 extern int zap_other_threads(struct task_struct *p);
342 extern struct sigqueue *sigqueue_alloc(void);
343 extern void sigqueue_free(struct sigqueue *);
344 extern int send_sigqueue(struct sigqueue *, struct pid *, enum pid_type);
345 extern int do_sigaction(int, struct k_sigaction *, struct k_sigaction *);
346 
347 static inline void clear_notify_signal(void)
348 {
349 	clear_thread_flag(TIF_NOTIFY_SIGNAL);
350 	smp_mb__after_atomic();
351 }
352 
353 /*
354  * Returns 'true' if kick_process() is needed to force a transition from
355  * user -> kernel to guarantee expedient run of TWA_SIGNAL based task_work.
356  */
357 static inline bool __set_notify_signal(struct task_struct *task)
358 {
359 	return !test_and_set_tsk_thread_flag(task, TIF_NOTIFY_SIGNAL) &&
360 	       !wake_up_state(task, TASK_INTERRUPTIBLE);
361 }
362 
363 /*
364  * Called to break out of interruptible wait loops, and enter the
365  * exit_to_user_mode_loop().
366  */
367 static inline void set_notify_signal(struct task_struct *task)
368 {
369 	if (__set_notify_signal(task))
370 		kick_process(task);
371 }
372 
373 static inline int restart_syscall(void)
374 {
375 	set_tsk_thread_flag(current, TIF_SIGPENDING);
376 	return -ERESTARTNOINTR;
377 }
378 
379 static inline int task_sigpending(struct task_struct *p)
380 {
381 	return unlikely(test_tsk_thread_flag(p,TIF_SIGPENDING));
382 }
383 
384 static inline int signal_pending(struct task_struct *p)
385 {
386 	/*
387 	 * TIF_NOTIFY_SIGNAL isn't really a signal, but it requires the same
388 	 * behavior in terms of ensuring that we break out of wait loops
389 	 * so that notify signal callbacks can be processed.
390 	 */
391 	if (unlikely(test_tsk_thread_flag(p, TIF_NOTIFY_SIGNAL)))
392 		return 1;
393 	return task_sigpending(p);
394 }
395 
396 static inline int __fatal_signal_pending(struct task_struct *p)
397 {
398 	return unlikely(sigismember(&p->pending.signal, SIGKILL));
399 }
400 
401 static inline int fatal_signal_pending(struct task_struct *p)
402 {
403 	return task_sigpending(p) && __fatal_signal_pending(p);
404 }
405 
406 static inline int signal_pending_state(unsigned int state, struct task_struct *p)
407 {
408 	if (!(state & (TASK_INTERRUPTIBLE | TASK_WAKEKILL)))
409 		return 0;
410 	if (!signal_pending(p))
411 		return 0;
412 
413 	return (state & TASK_INTERRUPTIBLE) || __fatal_signal_pending(p);
414 }
415 
416 /*
417  * This should only be used in fault handlers to decide whether we
418  * should stop the current fault routine to handle the signals
419  * instead, especially with the case where we've got interrupted with
420  * a VM_FAULT_RETRY.
421  */
422 static inline bool fault_signal_pending(vm_fault_t fault_flags,
423 					struct pt_regs *regs)
424 {
425 	return unlikely((fault_flags & VM_FAULT_RETRY) &&
426 			(fatal_signal_pending(current) ||
427 			 (user_mode(regs) && signal_pending(current))));
428 }
429 
430 /*
431  * Reevaluate whether the task has signals pending delivery.
432  * Wake the task if so.
433  * This is required every time the blocked sigset_t changes.
434  * callers must hold sighand->siglock.
435  */
436 extern void recalc_sigpending(void);
437 extern void calculate_sigpending(void);
438 
439 extern void signal_wake_up_state(struct task_struct *t, unsigned int state);
440 
441 static inline void signal_wake_up(struct task_struct *t, bool fatal)
442 {
443 	unsigned int state = 0;
444 	if (fatal && !(t->jobctl & JOBCTL_PTRACE_FROZEN)) {
445 		t->jobctl &= ~(JOBCTL_STOPPED | JOBCTL_TRACED);
446 		state = TASK_WAKEKILL | __TASK_TRACED;
447 	}
448 	signal_wake_up_state(t, state);
449 }
450 static inline void ptrace_signal_wake_up(struct task_struct *t, bool resume)
451 {
452 	unsigned int state = 0;
453 	if (resume) {
454 		t->jobctl &= ~JOBCTL_TRACED;
455 		state = __TASK_TRACED;
456 	}
457 	signal_wake_up_state(t, state);
458 }
459 
460 void task_join_group_stop(struct task_struct *task);
461 
462 #ifdef TIF_RESTORE_SIGMASK
463 /*
464  * Legacy restore_sigmask accessors.  These are inefficient on
465  * SMP architectures because they require atomic operations.
466  */
467 
468 /**
469  * set_restore_sigmask() - make sure saved_sigmask processing gets done
470  *
471  * This sets TIF_RESTORE_SIGMASK and ensures that the arch signal code
472  * will run before returning to user mode, to process the flag.  For
473  * all callers, TIF_SIGPENDING is already set or it's no harm to set
474  * it.  TIF_RESTORE_SIGMASK need not be in the set of bits that the
475  * arch code will notice on return to user mode, in case those bits
476  * are scarce.  We set TIF_SIGPENDING here to ensure that the arch
477  * signal code always gets run when TIF_RESTORE_SIGMASK is set.
478  */
479 static inline void set_restore_sigmask(void)
480 {
481 	set_thread_flag(TIF_RESTORE_SIGMASK);
482 }
483 
484 static inline void clear_tsk_restore_sigmask(struct task_struct *task)
485 {
486 	clear_tsk_thread_flag(task, TIF_RESTORE_SIGMASK);
487 }
488 
489 static inline void clear_restore_sigmask(void)
490 {
491 	clear_thread_flag(TIF_RESTORE_SIGMASK);
492 }
493 static inline bool test_tsk_restore_sigmask(struct task_struct *task)
494 {
495 	return test_tsk_thread_flag(task, TIF_RESTORE_SIGMASK);
496 }
497 static inline bool test_restore_sigmask(void)
498 {
499 	return test_thread_flag(TIF_RESTORE_SIGMASK);
500 }
501 static inline bool test_and_clear_restore_sigmask(void)
502 {
503 	return test_and_clear_thread_flag(TIF_RESTORE_SIGMASK);
504 }
505 
506 #else	/* TIF_RESTORE_SIGMASK */
507 
508 /* Higher-quality implementation, used if TIF_RESTORE_SIGMASK doesn't exist. */
509 static inline void set_restore_sigmask(void)
510 {
511 	current->restore_sigmask = true;
512 }
513 static inline void clear_tsk_restore_sigmask(struct task_struct *task)
514 {
515 	task->restore_sigmask = false;
516 }
517 static inline void clear_restore_sigmask(void)
518 {
519 	current->restore_sigmask = false;
520 }
521 static inline bool test_restore_sigmask(void)
522 {
523 	return current->restore_sigmask;
524 }
525 static inline bool test_tsk_restore_sigmask(struct task_struct *task)
526 {
527 	return task->restore_sigmask;
528 }
529 static inline bool test_and_clear_restore_sigmask(void)
530 {
531 	if (!current->restore_sigmask)
532 		return false;
533 	current->restore_sigmask = false;
534 	return true;
535 }
536 #endif
537 
538 static inline void restore_saved_sigmask(void)
539 {
540 	if (test_and_clear_restore_sigmask())
541 		__set_current_blocked(&current->saved_sigmask);
542 }
543 
544 extern int set_user_sigmask(const sigset_t __user *umask, size_t sigsetsize);
545 
546 static inline void restore_saved_sigmask_unless(bool interrupted)
547 {
548 	if (interrupted)
549 		WARN_ON(!signal_pending(current));
550 	else
551 		restore_saved_sigmask();
552 }
553 
554 static inline sigset_t *sigmask_to_save(void)
555 {
556 	sigset_t *res = &current->blocked;
557 	if (unlikely(test_restore_sigmask()))
558 		res = &current->saved_sigmask;
559 	return res;
560 }
561 
562 static inline int kill_cad_pid(int sig, int priv)
563 {
564 	return kill_pid(cad_pid, sig, priv);
565 }
566 
567 /* These can be the second arg to send_sig_info/send_group_sig_info.  */
568 #define SEND_SIG_NOINFO ((struct kernel_siginfo *) 0)
569 #define SEND_SIG_PRIV	((struct kernel_siginfo *) 1)
570 
571 static inline int __on_sig_stack(unsigned long sp)
572 {
573 #ifdef CONFIG_STACK_GROWSUP
574 	return sp >= current->sas_ss_sp &&
575 		sp - current->sas_ss_sp < current->sas_ss_size;
576 #else
577 	return sp > current->sas_ss_sp &&
578 		sp - current->sas_ss_sp <= current->sas_ss_size;
579 #endif
580 }
581 
582 /*
583  * True if we are on the alternate signal stack.
584  */
585 static inline int on_sig_stack(unsigned long sp)
586 {
587 	/*
588 	 * If the signal stack is SS_AUTODISARM then, by construction, we
589 	 * can't be on the signal stack unless user code deliberately set
590 	 * SS_AUTODISARM when we were already on it.
591 	 *
592 	 * This improves reliability: if user state gets corrupted such that
593 	 * the stack pointer points very close to the end of the signal stack,
594 	 * then this check will enable the signal to be handled anyway.
595 	 */
596 	if (current->sas_ss_flags & SS_AUTODISARM)
597 		return 0;
598 
599 	return __on_sig_stack(sp);
600 }
601 
602 static inline int sas_ss_flags(unsigned long sp)
603 {
604 	if (!current->sas_ss_size)
605 		return SS_DISABLE;
606 
607 	return on_sig_stack(sp) ? SS_ONSTACK : 0;
608 }
609 
610 static inline void sas_ss_reset(struct task_struct *p)
611 {
612 	p->sas_ss_sp = 0;
613 	p->sas_ss_size = 0;
614 	p->sas_ss_flags = SS_DISABLE;
615 }
616 
617 static inline unsigned long sigsp(unsigned long sp, struct ksignal *ksig)
618 {
619 	if (unlikely((ksig->ka.sa.sa_flags & SA_ONSTACK)) && ! sas_ss_flags(sp))
620 #ifdef CONFIG_STACK_GROWSUP
621 		return current->sas_ss_sp;
622 #else
623 		return current->sas_ss_sp + current->sas_ss_size;
624 #endif
625 	return sp;
626 }
627 
628 extern void __cleanup_sighand(struct sighand_struct *);
629 extern void flush_itimer_signals(void);
630 
631 #define tasklist_empty() \
632 	list_empty(&init_task.tasks)
633 
634 #define next_task(p) \
635 	list_entry_rcu((p)->tasks.next, struct task_struct, tasks)
636 
637 #define for_each_process(p) \
638 	for (p = &init_task ; (p = next_task(p)) != &init_task ; )
639 
640 extern bool current_is_single_threaded(void);
641 
642 /*
643  * Without tasklist/siglock it is only rcu-safe if g can't exit/exec,
644  * otherwise next_thread(t) will never reach g after list_del_rcu(g).
645  */
646 #define while_each_thread(g, t) \
647 	while ((t = next_thread(t)) != g)
648 
649 #define for_other_threads(p, t)	\
650 	for (t = p; (t = next_thread(t)) != p; )
651 
652 #define __for_each_thread(signal, t)	\
653 	list_for_each_entry_rcu(t, &(signal)->thread_head, thread_node, \
654 		lockdep_is_held(&tasklist_lock))
655 
656 #define for_each_thread(p, t)		\
657 	__for_each_thread((p)->signal, t)
658 
659 /* Careful: this is a double loop, 'break' won't work as expected. */
660 #define for_each_process_thread(p, t)	\
661 	for_each_process(p) for_each_thread(p, t)
662 
663 typedef int (*proc_visitor)(struct task_struct *p, void *data);
664 void walk_process_tree(struct task_struct *top, proc_visitor, void *);
665 
666 static inline
667 struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
668 {
669 	struct pid *pid;
670 	if (type == PIDTYPE_PID)
671 		pid = task_pid(task);
672 	else
673 		pid = task->signal->pids[type];
674 	return pid;
675 }
676 
677 static inline struct pid *task_tgid(struct task_struct *task)
678 {
679 	return task->signal->pids[PIDTYPE_TGID];
680 }
681 
682 /*
683  * Without tasklist or RCU lock it is not safe to dereference
684  * the result of task_pgrp/task_session even if task == current,
685  * we can race with another thread doing sys_setsid/sys_setpgid.
686  */
687 static inline struct pid *task_pgrp(struct task_struct *task)
688 {
689 	return task->signal->pids[PIDTYPE_PGID];
690 }
691 
692 static inline struct pid *task_session(struct task_struct *task)
693 {
694 	return task->signal->pids[PIDTYPE_SID];
695 }
696 
697 static inline int get_nr_threads(struct task_struct *task)
698 {
699 	return task->signal->nr_threads;
700 }
701 
702 static inline bool thread_group_leader(struct task_struct *p)
703 {
704 	return p->exit_signal >= 0;
705 }
706 
707 static inline
708 bool same_thread_group(struct task_struct *p1, struct task_struct *p2)
709 {
710 	return p1->signal == p2->signal;
711 }
712 
713 /*
714  * returns NULL if p is the last thread in the thread group
715  */
716 static inline struct task_struct *__next_thread(struct task_struct *p)
717 {
718 	return list_next_or_null_rcu(&p->signal->thread_head,
719 					&p->thread_node,
720 					struct task_struct,
721 					thread_node);
722 }
723 
724 static inline struct task_struct *next_thread(struct task_struct *p)
725 {
726 	return __next_thread(p) ?: p->group_leader;
727 }
728 
729 static inline int thread_group_empty(struct task_struct *p)
730 {
731 	return thread_group_leader(p) &&
732 	       list_is_last(&p->thread_node, &p->signal->thread_head);
733 }
734 
735 #define delay_group_leader(p) \
736 		(thread_group_leader(p) && !thread_group_empty(p))
737 
738 extern struct sighand_struct *__lock_task_sighand(struct task_struct *task,
739 							unsigned long *flags);
740 
741 static inline struct sighand_struct *lock_task_sighand(struct task_struct *task,
742 						       unsigned long *flags)
743 {
744 	struct sighand_struct *ret;
745 
746 	ret = __lock_task_sighand(task, flags);
747 	(void)__cond_lock(&task->sighand->siglock, ret);
748 	return ret;
749 }
750 
751 static inline void unlock_task_sighand(struct task_struct *task,
752 						unsigned long *flags)
753 {
754 	spin_unlock_irqrestore(&task->sighand->siglock, *flags);
755 }
756 
757 #ifdef CONFIG_LOCKDEP
758 extern void lockdep_assert_task_sighand_held(struct task_struct *task);
759 #else
760 static inline void lockdep_assert_task_sighand_held(struct task_struct *task) { }
761 #endif
762 
763 static inline unsigned long task_rlimit(const struct task_struct *task,
764 		unsigned int limit)
765 {
766 	return READ_ONCE(task->signal->rlim[limit].rlim_cur);
767 }
768 
769 static inline unsigned long task_rlimit_max(const struct task_struct *task,
770 		unsigned int limit)
771 {
772 	return READ_ONCE(task->signal->rlim[limit].rlim_max);
773 }
774 
775 static inline unsigned long rlimit(unsigned int limit)
776 {
777 	return task_rlimit(current, limit);
778 }
779 
780 static inline unsigned long rlimit_max(unsigned int limit)
781 {
782 	return task_rlimit_max(current, limit);
783 }
784 
785 #endif /* _LINUX_SCHED_SIGNAL_H */
786