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