1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_SCHED_TASK_H
3#define _LINUX_SCHED_TASK_H
4
5/*
6 * Interface between the scheduler and various task lifetime (fork()/exit())
7 * functionality:
8 */
9
10#include <linux/rcupdate.h>
11#include <linux/refcount.h>
12#include <linux/sched.h>
13#include <linux/uaccess.h>
14
15struct task_struct;
16struct rusage;
17union thread_union;
18struct css_set;
19
20/* All the bits taken by the old clone syscall. */
21#define CLONE_LEGACY_FLAGS 0xffffffffULL
22
23struct kernel_clone_args {
24	u64 flags;
25	int __user *pidfd;
26	int __user *child_tid;
27	int __user *parent_tid;
28	const char *name;
29	int exit_signal;
30	u32 kthread:1;
31	u32 io_thread:1;
32	u32 user_worker:1;
33	u32 no_files:1;
34	unsigned long stack;
35	unsigned long stack_size;
36	unsigned long tls;
37	pid_t *set_tid;
38	/* Number of elements in *set_tid */
39	size_t set_tid_size;
40	int cgroup;
41	int idle;
42	int (*fn)(void *);
43	void *fn_arg;
44	struct cgroup *cgrp;
45	struct css_set *cset;
46};
47
48/*
49 * This serializes "schedule()" and also protects
50 * the run-queue from deletions/modifications (but
51 * _adding_ to the beginning of the run-queue has
52 * a separate lock).
53 */
54extern rwlock_t tasklist_lock;
55extern spinlock_t mmlist_lock;
56
57extern union thread_union init_thread_union;
58extern struct task_struct init_task;
59
60extern int lockdep_tasklist_lock_is_held(void);
61
62extern asmlinkage void schedule_tail(struct task_struct *prev);
63extern void init_idle(struct task_struct *idle, int cpu);
64
65extern int sched_fork(unsigned long clone_flags, struct task_struct *p);
66extern void sched_cgroup_fork(struct task_struct *p, struct kernel_clone_args *kargs);
67extern void sched_post_fork(struct task_struct *p);
68extern void sched_dead(struct task_struct *p);
69
70void __noreturn do_task_dead(void);
71void __noreturn make_task_dead(int signr);
72
73extern void mm_cache_init(void);
74extern void proc_caches_init(void);
75
76extern void fork_init(void);
77
78extern void release_task(struct task_struct * p);
79
80extern int copy_thread(struct task_struct *, const struct kernel_clone_args *);
81
82extern void flush_thread(void);
83
84#ifdef CONFIG_HAVE_EXIT_THREAD
85extern void exit_thread(struct task_struct *tsk);
86#else
87static inline void exit_thread(struct task_struct *tsk)
88{
89}
90#endif
91extern __noreturn void do_group_exit(int);
92
93extern void exit_files(struct task_struct *);
94extern void exit_itimers(struct task_struct *);
95
96extern pid_t kernel_clone(struct kernel_clone_args *kargs);
97struct task_struct *copy_process(struct pid *pid, int trace, int node,
98				 struct kernel_clone_args *args);
99struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node);
100struct task_struct *fork_idle(int);
101extern pid_t kernel_thread(int (*fn)(void *), void *arg, const char *name,
102			    unsigned long flags);
103extern pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags);
104extern long kernel_wait4(pid_t, int __user *, int, struct rusage *);
105int kernel_wait(pid_t pid, int *stat);
106
107extern void free_task(struct task_struct *tsk);
108
109/* sched_exec is called by processes performing an exec */
110#ifdef CONFIG_SMP
111extern void sched_exec(void);
112#else
113#define sched_exec()   {}
114#endif
115
116static inline struct task_struct *get_task_struct(struct task_struct *t)
117{
118	refcount_inc(&t->usage);
119	return t;
120}
121
122extern void __put_task_struct(struct task_struct *t);
123extern void __put_task_struct_rcu_cb(struct rcu_head *rhp);
124
125static inline void put_task_struct(struct task_struct *t)
126{
127	if (!refcount_dec_and_test(&t->usage))
128		return;
129
130	/*
131	 * In !RT, it is always safe to call __put_task_struct().
132	 * Under RT, we can only call it in preemptible context.
133	 */
134	if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible()) {
135		static DEFINE_WAIT_OVERRIDE_MAP(put_task_map, LD_WAIT_SLEEP);
136
137		lock_map_acquire_try(&put_task_map);
138		__put_task_struct(t);
139		lock_map_release(&put_task_map);
140		return;
141	}
142
143	/*
144	 * under PREEMPT_RT, we can't call put_task_struct
145	 * in atomic context because it will indirectly
146	 * acquire sleeping locks.
147	 *
148	 * call_rcu() will schedule delayed_put_task_struct_rcu()
149	 * to be called in process context.
150	 *
151	 * __put_task_struct() is called when
152	 * refcount_dec_and_test(&t->usage) succeeds.
153	 *
154	 * This means that it can't "conflict" with
155	 * put_task_struct_rcu_user() which abuses ->rcu the same
156	 * way; rcu_users has a reference so task->usage can't be
157	 * zero after rcu_users 1 -> 0 transition.
158	 *
159	 * delayed_free_task() also uses ->rcu, but it is only called
160	 * when it fails to fork a process. Therefore, there is no
161	 * way it can conflict with put_task_struct().
162	 */
163	call_rcu(&t->rcu, __put_task_struct_rcu_cb);
164}
165
166DEFINE_FREE(put_task, struct task_struct *, if (_T) put_task_struct(_T))
167
168static inline void put_task_struct_many(struct task_struct *t, int nr)
169{
170	if (refcount_sub_and_test(nr, &t->usage))
171		__put_task_struct(t);
172}
173
174void put_task_struct_rcu_user(struct task_struct *task);
175
176/* Free all architecture-specific resources held by a thread. */
177void release_thread(struct task_struct *dead_task);
178
179#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
180extern int arch_task_struct_size __read_mostly;
181#else
182# define arch_task_struct_size (sizeof(struct task_struct))
183#endif
184
185#ifndef CONFIG_HAVE_ARCH_THREAD_STRUCT_WHITELIST
186/*
187 * If an architecture has not declared a thread_struct whitelist we
188 * must assume something there may need to be copied to userspace.
189 */
190static inline void arch_thread_struct_whitelist(unsigned long *offset,
191						unsigned long *size)
192{
193	*offset = 0;
194	/* Handle dynamically sized thread_struct. */
195	*size = arch_task_struct_size - offsetof(struct task_struct, thread);
196}
197#endif
198
199#ifdef CONFIG_VMAP_STACK
200static inline struct vm_struct *task_stack_vm_area(const struct task_struct *t)
201{
202	return t->stack_vm_area;
203}
204#else
205static inline struct vm_struct *task_stack_vm_area(const struct task_struct *t)
206{
207	return NULL;
208}
209#endif
210
211/*
212 * Protects ->fs, ->files, ->mm, ->group_info, ->comm, keyring
213 * subscriptions and synchronises with wait4().  Also used in procfs.  Also
214 * pins the final release of task.io_context.  Also protects ->cpuset and
215 * ->cgroup.subsys[]. And ->vfork_done. And ->sysvshm.shm_clist.
216 *
217 * Nests both inside and outside of read_lock(&tasklist_lock).
218 * It must not be nested with write_lock_irq(&tasklist_lock),
219 * neither inside nor outside.
220 */
221static inline void task_lock(struct task_struct *p)
222{
223	spin_lock(&p->alloc_lock);
224}
225
226static inline void task_unlock(struct task_struct *p)
227{
228	spin_unlock(&p->alloc_lock);
229}
230
231DEFINE_GUARD(task_lock, struct task_struct *, task_lock(_T), task_unlock(_T))
232
233#endif /* _LINUX_SCHED_TASK_H */
234