cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
Log | Files | Refs | README | LICENSE | sfeed.txt

signal.h (22220B)


      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/posix-timers.h>
     13#include <linux/mm_types.h>
     14#include <asm/ptrace.h>
     15
     16/*
     17 * Types defining task->signal and task->sighand and APIs using them:
     18 */
     19
     20struct sighand_struct {
     21	spinlock_t		siglock;
     22	refcount_t		count;
     23	wait_queue_head_t	signalfd_wqh;
     24	struct k_sigaction	action[_NSIG];
     25};
     26
     27/*
     28 * Per-process accounting stats:
     29 */
     30struct pacct_struct {
     31	int			ac_flag;
     32	long			ac_exitcode;
     33	unsigned long		ac_mem;
     34	u64			ac_utime, ac_stime;
     35	unsigned long		ac_minflt, ac_majflt;
     36};
     37
     38struct cpu_itimer {
     39	u64 expires;
     40	u64 incr;
     41};
     42
     43/*
     44 * This is the atomic variant of task_cputime, which can be used for
     45 * storing and updating task_cputime statistics without locking.
     46 */
     47struct task_cputime_atomic {
     48	atomic64_t utime;
     49	atomic64_t stime;
     50	atomic64_t sum_exec_runtime;
     51};
     52
     53#define INIT_CPUTIME_ATOMIC \
     54	(struct task_cputime_atomic) {				\
     55		.utime = ATOMIC64_INIT(0),			\
     56		.stime = ATOMIC64_INIT(0),			\
     57		.sum_exec_runtime = ATOMIC64_INIT(0),		\
     58	}
     59/**
     60 * struct thread_group_cputimer - thread group interval timer counts
     61 * @cputime_atomic:	atomic thread group interval timers.
     62 *
     63 * This structure contains the version of task_cputime, above, that is
     64 * used for thread group CPU timer calculations.
     65 */
     66struct thread_group_cputimer {
     67	struct task_cputime_atomic cputime_atomic;
     68};
     69
     70struct multiprocess_signals {
     71	sigset_t signal;
     72	struct hlist_node node;
     73};
     74
     75struct core_thread {
     76	struct task_struct *task;
     77	struct core_thread *next;
     78};
     79
     80struct core_state {
     81	atomic_t nr_threads;
     82	struct core_thread dumper;
     83	struct completion startup;
     84};
     85
     86/*
     87 * NOTE! "signal_struct" does not have its own
     88 * locking, because a shared signal_struct always
     89 * implies a shared sighand_struct, so locking
     90 * sighand_struct is always a proper superset of
     91 * the locking of signal_struct.
     92 */
     93struct signal_struct {
     94	refcount_t		sigcnt;
     95	atomic_t		live;
     96	int			nr_threads;
     97	struct list_head	thread_head;
     98
     99	wait_queue_head_t	wait_chldexit;	/* for wait4() */
    100
    101	/* current thread group signal load-balancing target: */
    102	struct task_struct	*curr_target;
    103
    104	/* shared signal handling: */
    105	struct sigpending	shared_pending;
    106
    107	/* For collecting multiprocess signals during fork */
    108	struct hlist_head	multiprocess;
    109
    110	/* thread group exit support */
    111	int			group_exit_code;
    112	/* notify group_exec_task when notify_count is less or equal to 0 */
    113	int			notify_count;
    114	struct task_struct	*group_exec_task;
    115
    116	/* thread group stop support, overloads group_exit_code too */
    117	int			group_stop_count;
    118	unsigned int		flags; /* see SIGNAL_* flags below */
    119
    120	struct core_state *core_state; /* coredumping support */
    121
    122	/*
    123	 * PR_SET_CHILD_SUBREAPER marks a process, like a service
    124	 * manager, to re-parent orphan (double-forking) child processes
    125	 * to this process instead of 'init'. The service manager is
    126	 * able to receive SIGCHLD signals and is able to investigate
    127	 * the process until it calls wait(). All children of this
    128	 * process will inherit a flag if they should look for a
    129	 * child_subreaper process at exit.
    130	 */
    131	unsigned int		is_child_subreaper:1;
    132	unsigned int		has_child_subreaper:1;
    133
    134#ifdef CONFIG_POSIX_TIMERS
    135
    136	/* POSIX.1b Interval Timers */
    137	int			posix_timer_id;
    138	struct list_head	posix_timers;
    139
    140	/* ITIMER_REAL timer for the process */
    141	struct hrtimer real_timer;
    142	ktime_t it_real_incr;
    143
    144	/*
    145	 * ITIMER_PROF and ITIMER_VIRTUAL timers for the process, we use
    146	 * CPUCLOCK_PROF and CPUCLOCK_VIRT for indexing array as these
    147	 * values are defined to 0 and 1 respectively
    148	 */
    149	struct cpu_itimer it[2];
    150
    151	/*
    152	 * Thread group totals for process CPU timers.
    153	 * See thread_group_cputimer(), et al, for details.
    154	 */
    155	struct thread_group_cputimer cputimer;
    156
    157#endif
    158	/* Empty if CONFIG_POSIX_TIMERS=n */
    159	struct posix_cputimers posix_cputimers;
    160
    161	/* PID/PID hash table linkage. */
    162	struct pid *pids[PIDTYPE_MAX];
    163
    164#ifdef CONFIG_NO_HZ_FULL
    165	atomic_t tick_dep_mask;
    166#endif
    167
    168	struct pid *tty_old_pgrp;
    169
    170	/* boolean value for session group leader */
    171	int leader;
    172
    173	struct tty_struct *tty; /* NULL if no tty */
    174
    175#ifdef CONFIG_SCHED_AUTOGROUP
    176	struct autogroup *autogroup;
    177#endif
    178	/*
    179	 * Cumulative resource counters for dead threads in the group,
    180	 * and for reaped dead child processes forked by this group.
    181	 * Live threads maintain their own counters and add to these
    182	 * in __exit_signal, except for the group leader.
    183	 */
    184	seqlock_t stats_lock;
    185	u64 utime, stime, cutime, cstime;
    186	u64 gtime;
    187	u64 cgtime;
    188	struct prev_cputime prev_cputime;
    189	unsigned long nvcsw, nivcsw, cnvcsw, cnivcsw;
    190	unsigned long min_flt, maj_flt, cmin_flt, cmaj_flt;
    191	unsigned long inblock, oublock, cinblock, coublock;
    192	unsigned long maxrss, cmaxrss;
    193	struct task_io_accounting ioac;
    194
    195	/*
    196	 * Cumulative ns of schedule CPU time fo dead threads in the
    197	 * group, not including a zombie group leader, (This only differs
    198	 * from jiffies_to_ns(utime + stime) if sched_clock uses something
    199	 * other than jiffies.)
    200	 */
    201	unsigned long long sum_sched_runtime;
    202
    203	/*
    204	 * We don't bother to synchronize most readers of this at all,
    205	 * because there is no reader checking a limit that actually needs
    206	 * to get both rlim_cur and rlim_max atomically, and either one
    207	 * alone is a single word that can safely be read normally.
    208	 * getrlimit/setrlimit use task_lock(current->group_leader) to
    209	 * protect this instead of the siglock, because they really
    210	 * have no need to disable irqs.
    211	 */
    212	struct rlimit rlim[RLIM_NLIMITS];
    213
    214#ifdef CONFIG_BSD_PROCESS_ACCT
    215	struct pacct_struct pacct;	/* per-process accounting information */
    216#endif
    217#ifdef CONFIG_TASKSTATS
    218	struct taskstats *stats;
    219#endif
    220#ifdef CONFIG_AUDIT
    221	unsigned audit_tty;
    222	struct tty_audit_buf *tty_audit_buf;
    223#endif
    224
    225	/*
    226	 * Thread is the potential origin of an oom condition; kill first on
    227	 * oom
    228	 */
    229	bool oom_flag_origin;
    230	short oom_score_adj;		/* OOM kill score adjustment */
    231	short oom_score_adj_min;	/* OOM kill score adjustment min value.
    232					 * Only settable by CAP_SYS_RESOURCE. */
    233	struct mm_struct *oom_mm;	/* recorded mm when the thread group got
    234					 * killed by the oom killer */
    235
    236	struct mutex cred_guard_mutex;	/* guard against foreign influences on
    237					 * credential calculations
    238					 * (notably. ptrace)
    239					 * Deprecated do not use in new code.
    240					 * Use exec_update_lock instead.
    241					 */
    242	struct rw_semaphore exec_update_lock;	/* Held while task_struct is
    243						 * being updated during exec,
    244						 * and may have inconsistent
    245						 * permissions.
    246						 */
    247} __randomize_layout;
    248
    249/*
    250 * Bits in flags field of signal_struct.
    251 */
    252#define SIGNAL_STOP_STOPPED	0x00000001 /* job control stop in effect */
    253#define SIGNAL_STOP_CONTINUED	0x00000002 /* SIGCONT since WCONTINUED reap */
    254#define SIGNAL_GROUP_EXIT	0x00000004 /* group exit in progress */
    255/*
    256 * Pending notifications to parent.
    257 */
    258#define SIGNAL_CLD_STOPPED	0x00000010
    259#define SIGNAL_CLD_CONTINUED	0x00000020
    260#define SIGNAL_CLD_MASK		(SIGNAL_CLD_STOPPED|SIGNAL_CLD_CONTINUED)
    261
    262#define SIGNAL_UNKILLABLE	0x00000040 /* for init: ignore fatal signals */
    263
    264#define SIGNAL_STOP_MASK (SIGNAL_CLD_MASK | SIGNAL_STOP_STOPPED | \
    265			  SIGNAL_STOP_CONTINUED)
    266
    267static inline void signal_set_stop_flags(struct signal_struct *sig,
    268					 unsigned int flags)
    269{
    270	WARN_ON(sig->flags & SIGNAL_GROUP_EXIT);
    271	sig->flags = (sig->flags & ~SIGNAL_STOP_MASK) | flags;
    272}
    273
    274extern void flush_signals(struct task_struct *);
    275extern void ignore_signals(struct task_struct *);
    276extern void flush_signal_handlers(struct task_struct *, int force_default);
    277extern int dequeue_signal(struct task_struct *task, sigset_t *mask,
    278			  kernel_siginfo_t *info, enum pid_type *type);
    279
    280static inline int kernel_dequeue_signal(void)
    281{
    282	struct task_struct *task = current;
    283	kernel_siginfo_t __info;
    284	enum pid_type __type;
    285	int ret;
    286
    287	spin_lock_irq(&task->sighand->siglock);
    288	ret = dequeue_signal(task, &task->blocked, &__info, &__type);
    289	spin_unlock_irq(&task->sighand->siglock);
    290
    291	return ret;
    292}
    293
    294static inline void kernel_signal_stop(void)
    295{
    296	spin_lock_irq(&current->sighand->siglock);
    297	if (current->jobctl & JOBCTL_STOP_DEQUEUED) {
    298		current->jobctl |= JOBCTL_STOPPED;
    299		set_special_state(TASK_STOPPED);
    300	}
    301	spin_unlock_irq(&current->sighand->siglock);
    302
    303	schedule();
    304}
    305#ifdef __ia64__
    306# define ___ARCH_SI_IA64(_a1, _a2, _a3) , _a1, _a2, _a3
    307#else
    308# define ___ARCH_SI_IA64(_a1, _a2, _a3)
    309#endif
    310
    311int force_sig_fault_to_task(int sig, int code, void __user *addr
    312	___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr)
    313	, struct task_struct *t);
    314int force_sig_fault(int sig, int code, void __user *addr
    315	___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr));
    316int send_sig_fault(int sig, int code, void __user *addr
    317	___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr)
    318	, struct task_struct *t);
    319
    320int force_sig_mceerr(int code, void __user *, short);
    321int send_sig_mceerr(int code, void __user *, short, struct task_struct *);
    322
    323int force_sig_bnderr(void __user *addr, void __user *lower, void __user *upper);
    324int force_sig_pkuerr(void __user *addr, u32 pkey);
    325int send_sig_perf(void __user *addr, u32 type, u64 sig_data);
    326
    327int force_sig_ptrace_errno_trap(int errno, void __user *addr);
    328int force_sig_fault_trapno(int sig, int code, void __user *addr, int trapno);
    329int send_sig_fault_trapno(int sig, int code, void __user *addr, int trapno,
    330			struct task_struct *t);
    331int force_sig_seccomp(int syscall, int reason, bool force_coredump);
    332
    333extern int send_sig_info(int, struct kernel_siginfo *, struct task_struct *);
    334extern void force_sigsegv(int sig);
    335extern int force_sig_info(struct kernel_siginfo *);
    336extern int __kill_pgrp_info(int sig, struct kernel_siginfo *info, struct pid *pgrp);
    337extern int kill_pid_info(int sig, struct kernel_siginfo *info, struct pid *pid);
    338extern int kill_pid_usb_asyncio(int sig, int errno, sigval_t addr, struct pid *,
    339				const struct cred *);
    340extern int kill_pgrp(struct pid *pid, int sig, int priv);
    341extern int kill_pid(struct pid *pid, int sig, int priv);
    342extern __must_check bool do_notify_parent(struct task_struct *, int);
    343extern void __wake_up_parent(struct task_struct *p, struct task_struct *parent);
    344extern void force_sig(int);
    345extern void force_fatal_sig(int);
    346extern void force_exit_sig(int);
    347extern int send_sig(int, struct task_struct *, int);
    348extern int zap_other_threads(struct task_struct *p);
    349extern struct sigqueue *sigqueue_alloc(void);
    350extern void sigqueue_free(struct sigqueue *);
    351extern int send_sigqueue(struct sigqueue *, struct pid *, enum pid_type);
    352extern int do_sigaction(int, struct k_sigaction *, struct k_sigaction *);
    353
    354static inline void clear_notify_signal(void)
    355{
    356	clear_thread_flag(TIF_NOTIFY_SIGNAL);
    357	smp_mb__after_atomic();
    358}
    359
    360/*
    361 * Returns 'true' if kick_process() is needed to force a transition from
    362 * user -> kernel to guarantee expedient run of TWA_SIGNAL based task_work.
    363 */
    364static inline bool __set_notify_signal(struct task_struct *task)
    365{
    366	return !test_and_set_tsk_thread_flag(task, TIF_NOTIFY_SIGNAL) &&
    367	       !wake_up_state(task, TASK_INTERRUPTIBLE);
    368}
    369
    370/*
    371 * Called to break out of interruptible wait loops, and enter the
    372 * exit_to_user_mode_loop().
    373 */
    374static inline void set_notify_signal(struct task_struct *task)
    375{
    376	if (__set_notify_signal(task))
    377		kick_process(task);
    378}
    379
    380static inline int restart_syscall(void)
    381{
    382	set_tsk_thread_flag(current, TIF_SIGPENDING);
    383	return -ERESTARTNOINTR;
    384}
    385
    386static inline int task_sigpending(struct task_struct *p)
    387{
    388	return unlikely(test_tsk_thread_flag(p,TIF_SIGPENDING));
    389}
    390
    391static inline int signal_pending(struct task_struct *p)
    392{
    393	/*
    394	 * TIF_NOTIFY_SIGNAL isn't really a signal, but it requires the same
    395	 * behavior in terms of ensuring that we break out of wait loops
    396	 * so that notify signal callbacks can be processed.
    397	 */
    398	if (unlikely(test_tsk_thread_flag(p, TIF_NOTIFY_SIGNAL)))
    399		return 1;
    400	return task_sigpending(p);
    401}
    402
    403static inline int __fatal_signal_pending(struct task_struct *p)
    404{
    405	return unlikely(sigismember(&p->pending.signal, SIGKILL));
    406}
    407
    408static inline int fatal_signal_pending(struct task_struct *p)
    409{
    410	return task_sigpending(p) && __fatal_signal_pending(p);
    411}
    412
    413static inline int signal_pending_state(unsigned int state, struct task_struct *p)
    414{
    415	if (!(state & (TASK_INTERRUPTIBLE | TASK_WAKEKILL)))
    416		return 0;
    417	if (!signal_pending(p))
    418		return 0;
    419
    420	return (state & TASK_INTERRUPTIBLE) || __fatal_signal_pending(p);
    421}
    422
    423/*
    424 * This should only be used in fault handlers to decide whether we
    425 * should stop the current fault routine to handle the signals
    426 * instead, especially with the case where we've got interrupted with
    427 * a VM_FAULT_RETRY.
    428 */
    429static inline bool fault_signal_pending(vm_fault_t fault_flags,
    430					struct pt_regs *regs)
    431{
    432	return unlikely((fault_flags & VM_FAULT_RETRY) &&
    433			(fatal_signal_pending(current) ||
    434			 (user_mode(regs) && signal_pending(current))));
    435}
    436
    437/*
    438 * Reevaluate whether the task has signals pending delivery.
    439 * Wake the task if so.
    440 * This is required every time the blocked sigset_t changes.
    441 * callers must hold sighand->siglock.
    442 */
    443extern void recalc_sigpending_and_wake(struct task_struct *t);
    444extern void recalc_sigpending(void);
    445extern void calculate_sigpending(void);
    446
    447extern void signal_wake_up_state(struct task_struct *t, unsigned int state);
    448
    449static inline void signal_wake_up(struct task_struct *t, bool fatal)
    450{
    451	unsigned int state = 0;
    452	if (fatal && !(t->jobctl & JOBCTL_PTRACE_FROZEN)) {
    453		t->jobctl &= ~(JOBCTL_STOPPED | JOBCTL_TRACED);
    454		state = TASK_WAKEKILL | __TASK_TRACED;
    455	}
    456	signal_wake_up_state(t, state);
    457}
    458static inline void ptrace_signal_wake_up(struct task_struct *t, bool resume)
    459{
    460	unsigned int state = 0;
    461	if (resume) {
    462		t->jobctl &= ~JOBCTL_TRACED;
    463		state = __TASK_TRACED;
    464	}
    465	signal_wake_up_state(t, state);
    466}
    467
    468void task_join_group_stop(struct task_struct *task);
    469
    470#ifdef TIF_RESTORE_SIGMASK
    471/*
    472 * Legacy restore_sigmask accessors.  These are inefficient on
    473 * SMP architectures because they require atomic operations.
    474 */
    475
    476/**
    477 * set_restore_sigmask() - make sure saved_sigmask processing gets done
    478 *
    479 * This sets TIF_RESTORE_SIGMASK and ensures that the arch signal code
    480 * will run before returning to user mode, to process the flag.  For
    481 * all callers, TIF_SIGPENDING is already set or it's no harm to set
    482 * it.  TIF_RESTORE_SIGMASK need not be in the set of bits that the
    483 * arch code will notice on return to user mode, in case those bits
    484 * are scarce.  We set TIF_SIGPENDING here to ensure that the arch
    485 * signal code always gets run when TIF_RESTORE_SIGMASK is set.
    486 */
    487static inline void set_restore_sigmask(void)
    488{
    489	set_thread_flag(TIF_RESTORE_SIGMASK);
    490}
    491
    492static inline void clear_tsk_restore_sigmask(struct task_struct *task)
    493{
    494	clear_tsk_thread_flag(task, TIF_RESTORE_SIGMASK);
    495}
    496
    497static inline void clear_restore_sigmask(void)
    498{
    499	clear_thread_flag(TIF_RESTORE_SIGMASK);
    500}
    501static inline bool test_tsk_restore_sigmask(struct task_struct *task)
    502{
    503	return test_tsk_thread_flag(task, TIF_RESTORE_SIGMASK);
    504}
    505static inline bool test_restore_sigmask(void)
    506{
    507	return test_thread_flag(TIF_RESTORE_SIGMASK);
    508}
    509static inline bool test_and_clear_restore_sigmask(void)
    510{
    511	return test_and_clear_thread_flag(TIF_RESTORE_SIGMASK);
    512}
    513
    514#else	/* TIF_RESTORE_SIGMASK */
    515
    516/* Higher-quality implementation, used if TIF_RESTORE_SIGMASK doesn't exist. */
    517static inline void set_restore_sigmask(void)
    518{
    519	current->restore_sigmask = true;
    520}
    521static inline void clear_tsk_restore_sigmask(struct task_struct *task)
    522{
    523	task->restore_sigmask = false;
    524}
    525static inline void clear_restore_sigmask(void)
    526{
    527	current->restore_sigmask = false;
    528}
    529static inline bool test_restore_sigmask(void)
    530{
    531	return current->restore_sigmask;
    532}
    533static inline bool test_tsk_restore_sigmask(struct task_struct *task)
    534{
    535	return task->restore_sigmask;
    536}
    537static inline bool test_and_clear_restore_sigmask(void)
    538{
    539	if (!current->restore_sigmask)
    540		return false;
    541	current->restore_sigmask = false;
    542	return true;
    543}
    544#endif
    545
    546static inline void restore_saved_sigmask(void)
    547{
    548	if (test_and_clear_restore_sigmask())
    549		__set_current_blocked(&current->saved_sigmask);
    550}
    551
    552extern int set_user_sigmask(const sigset_t __user *umask, size_t sigsetsize);
    553
    554static inline void restore_saved_sigmask_unless(bool interrupted)
    555{
    556	if (interrupted)
    557		WARN_ON(!signal_pending(current));
    558	else
    559		restore_saved_sigmask();
    560}
    561
    562static inline sigset_t *sigmask_to_save(void)
    563{
    564	sigset_t *res = &current->blocked;
    565	if (unlikely(test_restore_sigmask()))
    566		res = &current->saved_sigmask;
    567	return res;
    568}
    569
    570static inline int kill_cad_pid(int sig, int priv)
    571{
    572	return kill_pid(cad_pid, sig, priv);
    573}
    574
    575/* These can be the second arg to send_sig_info/send_group_sig_info.  */
    576#define SEND_SIG_NOINFO ((struct kernel_siginfo *) 0)
    577#define SEND_SIG_PRIV	((struct kernel_siginfo *) 1)
    578
    579static inline int __on_sig_stack(unsigned long sp)
    580{
    581#ifdef CONFIG_STACK_GROWSUP
    582	return sp >= current->sas_ss_sp &&
    583		sp - current->sas_ss_sp < current->sas_ss_size;
    584#else
    585	return sp > current->sas_ss_sp &&
    586		sp - current->sas_ss_sp <= current->sas_ss_size;
    587#endif
    588}
    589
    590/*
    591 * True if we are on the alternate signal stack.
    592 */
    593static inline int on_sig_stack(unsigned long sp)
    594{
    595	/*
    596	 * If the signal stack is SS_AUTODISARM then, by construction, we
    597	 * can't be on the signal stack unless user code deliberately set
    598	 * SS_AUTODISARM when we were already on it.
    599	 *
    600	 * This improves reliability: if user state gets corrupted such that
    601	 * the stack pointer points very close to the end of the signal stack,
    602	 * then this check will enable the signal to be handled anyway.
    603	 */
    604	if (current->sas_ss_flags & SS_AUTODISARM)
    605		return 0;
    606
    607	return __on_sig_stack(sp);
    608}
    609
    610static inline int sas_ss_flags(unsigned long sp)
    611{
    612	if (!current->sas_ss_size)
    613		return SS_DISABLE;
    614
    615	return on_sig_stack(sp) ? SS_ONSTACK : 0;
    616}
    617
    618static inline void sas_ss_reset(struct task_struct *p)
    619{
    620	p->sas_ss_sp = 0;
    621	p->sas_ss_size = 0;
    622	p->sas_ss_flags = SS_DISABLE;
    623}
    624
    625static inline unsigned long sigsp(unsigned long sp, struct ksignal *ksig)
    626{
    627	if (unlikely((ksig->ka.sa.sa_flags & SA_ONSTACK)) && ! sas_ss_flags(sp))
    628#ifdef CONFIG_STACK_GROWSUP
    629		return current->sas_ss_sp;
    630#else
    631		return current->sas_ss_sp + current->sas_ss_size;
    632#endif
    633	return sp;
    634}
    635
    636extern void __cleanup_sighand(struct sighand_struct *);
    637extern void flush_itimer_signals(void);
    638
    639#define tasklist_empty() \
    640	list_empty(&init_task.tasks)
    641
    642#define next_task(p) \
    643	list_entry_rcu((p)->tasks.next, struct task_struct, tasks)
    644
    645#define for_each_process(p) \
    646	for (p = &init_task ; (p = next_task(p)) != &init_task ; )
    647
    648extern bool current_is_single_threaded(void);
    649
    650/*
    651 * Careful: do_each_thread/while_each_thread is a double loop so
    652 *          'break' will not work as expected - use goto instead.
    653 */
    654#define do_each_thread(g, t) \
    655	for (g = t = &init_task ; (g = t = next_task(g)) != &init_task ; ) do
    656
    657#define while_each_thread(g, t) \
    658	while ((t = next_thread(t)) != g)
    659
    660#define __for_each_thread(signal, t)	\
    661	list_for_each_entry_rcu(t, &(signal)->thread_head, thread_node)
    662
    663#define for_each_thread(p, t)		\
    664	__for_each_thread((p)->signal, t)
    665
    666/* Careful: this is a double loop, 'break' won't work as expected. */
    667#define for_each_process_thread(p, t)	\
    668	for_each_process(p) for_each_thread(p, t)
    669
    670typedef int (*proc_visitor)(struct task_struct *p, void *data);
    671void walk_process_tree(struct task_struct *top, proc_visitor, void *);
    672
    673static inline
    674struct pid *task_pid_type(struct task_struct *task, enum pid_type type)
    675{
    676	struct pid *pid;
    677	if (type == PIDTYPE_PID)
    678		pid = task_pid(task);
    679	else
    680		pid = task->signal->pids[type];
    681	return pid;
    682}
    683
    684static inline struct pid *task_tgid(struct task_struct *task)
    685{
    686	return task->signal->pids[PIDTYPE_TGID];
    687}
    688
    689/*
    690 * Without tasklist or RCU lock it is not safe to dereference
    691 * the result of task_pgrp/task_session even if task == current,
    692 * we can race with another thread doing sys_setsid/sys_setpgid.
    693 */
    694static inline struct pid *task_pgrp(struct task_struct *task)
    695{
    696	return task->signal->pids[PIDTYPE_PGID];
    697}
    698
    699static inline struct pid *task_session(struct task_struct *task)
    700{
    701	return task->signal->pids[PIDTYPE_SID];
    702}
    703
    704static inline int get_nr_threads(struct task_struct *task)
    705{
    706	return task->signal->nr_threads;
    707}
    708
    709static inline bool thread_group_leader(struct task_struct *p)
    710{
    711	return p->exit_signal >= 0;
    712}
    713
    714static inline
    715bool same_thread_group(struct task_struct *p1, struct task_struct *p2)
    716{
    717	return p1->signal == p2->signal;
    718}
    719
    720static inline struct task_struct *next_thread(const struct task_struct *p)
    721{
    722	return list_entry_rcu(p->thread_group.next,
    723			      struct task_struct, thread_group);
    724}
    725
    726static inline int thread_group_empty(struct task_struct *p)
    727{
    728	return list_empty(&p->thread_group);
    729}
    730
    731#define delay_group_leader(p) \
    732		(thread_group_leader(p) && !thread_group_empty(p))
    733
    734extern bool thread_group_exited(struct pid *pid);
    735
    736extern struct sighand_struct *__lock_task_sighand(struct task_struct *task,
    737							unsigned long *flags);
    738
    739static inline struct sighand_struct *lock_task_sighand(struct task_struct *task,
    740						       unsigned long *flags)
    741{
    742	struct sighand_struct *ret;
    743
    744	ret = __lock_task_sighand(task, flags);
    745	(void)__cond_lock(&task->sighand->siglock, ret);
    746	return ret;
    747}
    748
    749static inline void unlock_task_sighand(struct task_struct *task,
    750						unsigned long *flags)
    751{
    752	spin_unlock_irqrestore(&task->sighand->siglock, *flags);
    753}
    754
    755#ifdef CONFIG_LOCKDEP
    756extern void lockdep_assert_task_sighand_held(struct task_struct *task);
    757#else
    758static inline void lockdep_assert_task_sighand_held(struct task_struct *task) { }
    759#endif
    760
    761static inline unsigned long task_rlimit(const struct task_struct *task,
    762		unsigned int limit)
    763{
    764	return READ_ONCE(task->signal->rlim[limit].rlim_cur);
    765}
    766
    767static inline unsigned long task_rlimit_max(const struct task_struct *task,
    768		unsigned int limit)
    769{
    770	return READ_ONCE(task->signal->rlim[limit].rlim_max);
    771}
    772
    773static inline unsigned long rlimit(unsigned int limit)
    774{
    775	return task_rlimit(current, limit);
    776}
    777
    778static inline unsigned long rlimit_max(unsigned int limit)
    779{
    780	return task_rlimit_max(current, limit);
    781}
    782
    783#endif /* _LINUX_SCHED_SIGNAL_H */