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 unsigned int kill_seq;
47};
48
49/*
50 * This serializes "schedule()" and also protects
51 * the run-queue from deletions/modifications (but
52 * _adding_ to the beginning of the run-queue has
53 * a separate lock).
54 */
55extern rwlock_t tasklist_lock;
56extern spinlock_t mmlist_lock;
57
58extern union thread_union init_thread_union;
59extern struct task_struct init_task;
60
61extern int lockdep_tasklist_lock_is_held(void);
62
63extern asmlinkage void schedule_tail(struct task_struct *prev);
64extern void init_idle(struct task_struct *idle, int cpu);
65
66extern int sched_fork(unsigned long clone_flags, struct task_struct *p);
67extern int sched_cgroup_fork(struct task_struct *p, struct kernel_clone_args *kargs);
68extern void sched_cancel_fork(struct task_struct *p);
69extern void sched_post_fork(struct task_struct *p);
70extern void sched_dead(struct task_struct *p);
71
72void __noreturn do_task_dead(void);
73void __noreturn make_task_dead(int signr);
74
75extern void mm_cache_init(void);
76extern void proc_caches_init(void);
77
78extern void fork_init(void);
79
80extern void release_task(struct task_struct * p);
81
82extern int copy_thread(struct task_struct *, const struct kernel_clone_args *);
83
84extern void flush_thread(void);
85
86#ifdef CONFIG_HAVE_EXIT_THREAD
87extern void exit_thread(struct task_struct *tsk);
88#else
89static inline void exit_thread(struct task_struct *tsk)
90{
91}
92#endif
93extern __noreturn void do_group_exit(int);
94
95extern void exit_files(struct task_struct *);
96extern void exit_itimers(struct task_struct *);
97
98extern pid_t kernel_clone(struct kernel_clone_args *kargs);
99struct task_struct *copy_process(struct pid *pid, int trace, int node,
100 struct kernel_clone_args *args);
101struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node);
102struct task_struct *fork_idle(int);
103extern pid_t kernel_thread(int (*fn)(void *), void *arg, const char *name,
104 unsigned long flags);
105extern pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags);
106extern long kernel_wait4(pid_t, int __user *, int, struct rusage *);
107int kernel_wait(pid_t pid, int *stat);
108
109extern void free_task(struct task_struct *tsk);
110
111/* sched_exec is called by processes performing an exec */
112#ifdef CONFIG_SMP
113extern void sched_exec(void);
114#else
115#define sched_exec() {}
116#endif
117
118static inline struct task_struct *get_task_struct(struct task_struct *t)
119{
120 refcount_inc(r: &t->usage);
121 return t;
122}
123
124static inline struct task_struct *tryget_task_struct(struct task_struct *t)
125{
126 return refcount_inc_not_zero(r: &t->usage) ? t : NULL;
127}
128
129extern void __put_task_struct(struct task_struct *t);
130extern void __put_task_struct_rcu_cb(struct rcu_head *rhp);
131
132static inline void put_task_struct(struct task_struct *t)
133{
134 if (!refcount_dec_and_test(r: &t->usage))
135 return;
136
137 /*
138 * In !RT, it is always safe to call __put_task_struct().
139 * Under RT, we can only call it in preemptible context.
140 */
141 if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible()) {
142 static DEFINE_WAIT_OVERRIDE_MAP(put_task_map, LD_WAIT_SLEEP);
143
144 lock_map_acquire_try(&put_task_map);
145 __put_task_struct(t);
146 lock_map_release(&put_task_map);
147 return;
148 }
149
150 /*
151 * under PREEMPT_RT, we can't call put_task_struct
152 * in atomic context because it will indirectly
153 * acquire sleeping locks.
154 *
155 * call_rcu() will schedule delayed_put_task_struct_rcu()
156 * to be called in process context.
157 *
158 * __put_task_struct() is called when
159 * refcount_dec_and_test(&t->usage) succeeds.
160 *
161 * This means that it can't "conflict" with
162 * put_task_struct_rcu_user() which abuses ->rcu the same
163 * way; rcu_users has a reference so task->usage can't be
164 * zero after rcu_users 1 -> 0 transition.
165 *
166 * delayed_free_task() also uses ->rcu, but it is only called
167 * when it fails to fork a process. Therefore, there is no
168 * way it can conflict with put_task_struct().
169 */
170 call_rcu(head: &t->rcu, func: __put_task_struct_rcu_cb);
171}
172
173DEFINE_FREE(put_task, struct task_struct *, if (_T) put_task_struct(_T))
174
175static inline void put_task_struct_many(struct task_struct *t, int nr)
176{
177 if (refcount_sub_and_test(i: nr, r: &t->usage))
178 __put_task_struct(t);
179}
180
181void put_task_struct_rcu_user(struct task_struct *task);
182
183/* Free all architecture-specific resources held by a thread. */
184void release_thread(struct task_struct *dead_task);
185
186#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
187extern int arch_task_struct_size __read_mostly;
188#else
189# define arch_task_struct_size (sizeof(struct task_struct))
190#endif
191
192#ifndef CONFIG_HAVE_ARCH_THREAD_STRUCT_WHITELIST
193/*
194 * If an architecture has not declared a thread_struct whitelist we
195 * must assume something there may need to be copied to userspace.
196 */
197static inline void arch_thread_struct_whitelist(unsigned long *offset,
198 unsigned long *size)
199{
200 *offset = 0;
201 /* Handle dynamically sized thread_struct. */
202 *size = arch_task_struct_size - offsetof(struct task_struct, thread);
203}
204#endif
205
206#ifdef CONFIG_VMAP_STACK
207static inline struct vm_struct *task_stack_vm_area(const struct task_struct *t)
208{
209 return t->stack_vm_area;
210}
211#else
212static inline struct vm_struct *task_stack_vm_area(const struct task_struct *t)
213{
214 return NULL;
215}
216#endif
217
218/*
219 * Protects ->fs, ->files, ->mm, ->group_info, ->comm, keyring
220 * subscriptions and synchronises with wait4(). Also used in procfs. Also
221 * pins the final release of task.io_context. Also protects ->cpuset and
222 * ->cgroup.subsys[]. And ->vfork_done. And ->sysvshm.shm_clist.
223 *
224 * Nests both inside and outside of read_lock(&tasklist_lock).
225 * It must not be nested with write_lock_irq(&tasklist_lock),
226 * neither inside nor outside.
227 */
228static inline void task_lock(struct task_struct *p)
229{
230 spin_lock(lock: &p->alloc_lock);
231}
232
233static inline void task_unlock(struct task_struct *p)
234{
235 spin_unlock(lock: &p->alloc_lock);
236}
237
238DEFINE_GUARD(task_lock, struct task_struct *, task_lock(_T), task_unlock(_T))
239
240#endif /* _LINUX_SCHED_TASK_H */
241

source code of linux/include/linux/sched/task.h