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