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