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 15 struct task_struct; 16 struct rusage; 17 union thread_union; 18 struct css_set; 19 20 /* All the bits taken by the old clone syscall. */ 21 #define CLONE_LEGACY_FLAGS 0xffffffffULL 22 23 struct 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 */ 54 extern rwlock_t tasklist_lock; 55 extern spinlock_t mmlist_lock; 56 57 extern union thread_union init_thread_union; 58 extern struct task_struct init_task; 59 60 extern int lockdep_tasklist_lock_is_held(void); 61 62 extern asmlinkage void schedule_tail(struct task_struct *prev); 63 extern void init_idle(struct task_struct *idle, int cpu); 64 65 extern int sched_fork(unsigned long clone_flags, struct task_struct *p); 66 extern int sched_cgroup_fork(struct task_struct *p, struct kernel_clone_args *kargs); 67 extern void sched_cancel_fork(struct task_struct *p); 68 extern void sched_post_fork(struct task_struct *p); 69 extern void sched_dead(struct task_struct *p); 70 71 void __noreturn do_task_dead(void); 72 void __noreturn make_task_dead(int signr); 73 74 extern void mm_cache_init(void); 75 extern void proc_caches_init(void); 76 77 extern void fork_init(void); 78 79 extern void release_task(struct task_struct * p); 80 81 extern int copy_thread(struct task_struct *, const struct kernel_clone_args *); 82 83 extern void flush_thread(void); 84 85 #ifdef CONFIG_HAVE_EXIT_THREAD 86 extern void exit_thread(struct task_struct *tsk); 87 #else 88 static inline void exit_thread(struct task_struct *tsk) 89 { 90 } 91 #endif 92 extern __noreturn void do_group_exit(int); 93 94 extern void exit_files(struct task_struct *); 95 extern void exit_itimers(struct task_struct *); 96 97 extern pid_t kernel_clone(struct kernel_clone_args *kargs); 98 struct task_struct *copy_process(struct pid *pid, int trace, int node, 99 struct kernel_clone_args *args); 100 struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node); 101 struct task_struct *fork_idle(int); 102 extern pid_t kernel_thread(int (*fn)(void *), void *arg, const char *name, 103 unsigned long flags); 104 extern pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags); 105 extern long kernel_wait4(pid_t, int __user *, int, struct rusage *); 106 int kernel_wait(pid_t pid, int *stat); 107 108 extern void free_task(struct task_struct *tsk); 109 110 /* sched_exec is called by processes performing an exec */ 111 #ifdef CONFIG_SMP 112 extern void sched_exec(void); 113 #else 114 #define sched_exec() {} 115 #endif 116 117 static inline struct task_struct *get_task_struct(struct task_struct *t) 118 { 119 refcount_inc(&t->usage); 120 return t; 121 } 122 123 extern void __put_task_struct(struct task_struct *t); 124 extern void __put_task_struct_rcu_cb(struct rcu_head *rhp); 125 126 static inline void put_task_struct(struct task_struct *t) 127 { 128 if (!refcount_dec_and_test(&t->usage)) 129 return; 130 131 /* 132 * In !RT, it is always safe to call __put_task_struct(). 133 * Under RT, we can only call it in preemptible context. 134 */ 135 if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible()) { 136 static DEFINE_WAIT_OVERRIDE_MAP(put_task_map, LD_WAIT_SLEEP); 137 138 lock_map_acquire_try(&put_task_map); 139 __put_task_struct(t); 140 lock_map_release(&put_task_map); 141 return; 142 } 143 144 /* 145 * under PREEMPT_RT, we can't call put_task_struct 146 * in atomic context because it will indirectly 147 * acquire sleeping locks. 148 * 149 * call_rcu() will schedule delayed_put_task_struct_rcu() 150 * to be called in process context. 151 * 152 * __put_task_struct() is called when 153 * refcount_dec_and_test(&t->usage) succeeds. 154 * 155 * This means that it can't "conflict" with 156 * put_task_struct_rcu_user() which abuses ->rcu the same 157 * way; rcu_users has a reference so task->usage can't be 158 * zero after rcu_users 1 -> 0 transition. 159 * 160 * delayed_free_task() also uses ->rcu, but it is only called 161 * when it fails to fork a process. Therefore, there is no 162 * way it can conflict with put_task_struct(). 163 */ 164 call_rcu(&t->rcu, __put_task_struct_rcu_cb); 165 } 166 167 DEFINE_FREE(put_task, struct task_struct *, if (_T) put_task_struct(_T)) 168 169 static inline void put_task_struct_many(struct task_struct *t, int nr) 170 { 171 if (refcount_sub_and_test(nr, &t->usage)) 172 __put_task_struct(t); 173 } 174 175 void put_task_struct_rcu_user(struct task_struct *task); 176 177 /* Free all architecture-specific resources held by a thread. */ 178 void release_thread(struct task_struct *dead_task); 179 180 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT 181 extern int arch_task_struct_size __read_mostly; 182 #else 183 # define arch_task_struct_size (sizeof(struct task_struct)) 184 #endif 185 186 #ifndef CONFIG_HAVE_ARCH_THREAD_STRUCT_WHITELIST 187 /* 188 * If an architecture has not declared a thread_struct whitelist we 189 * must assume something there may need to be copied to userspace. 190 */ 191 static inline void arch_thread_struct_whitelist(unsigned long *offset, 192 unsigned long *size) 193 { 194 *offset = 0; 195 /* Handle dynamically sized thread_struct. */ 196 *size = arch_task_struct_size - offsetof(struct task_struct, thread); 197 } 198 #endif 199 200 #ifdef CONFIG_VMAP_STACK 201 static inline struct vm_struct *task_stack_vm_area(const struct task_struct *t) 202 { 203 return t->stack_vm_area; 204 } 205 #else 206 static inline struct vm_struct *task_stack_vm_area(const struct task_struct *t) 207 { 208 return NULL; 209 } 210 #endif 211 212 /* 213 * Protects ->fs, ->files, ->mm, ->group_info, ->comm, keyring 214 * subscriptions and synchronises with wait4(). Also used in procfs. Also 215 * pins the final release of task.io_context. Also protects ->cpuset and 216 * ->cgroup.subsys[]. And ->vfork_done. And ->sysvshm.shm_clist. 217 * 218 * Nests both inside and outside of read_lock(&tasklist_lock). 219 * It must not be nested with write_lock_irq(&tasklist_lock), 220 * neither inside nor outside. 221 */ 222 static inline void task_lock(struct task_struct *p) 223 { 224 spin_lock(&p->alloc_lock); 225 } 226 227 static inline void task_unlock(struct task_struct *p) 228 { 229 spin_unlock(&p->alloc_lock); 230 } 231 232 DEFINE_GUARD(task_lock, struct task_struct *, task_lock(_T), task_unlock(_T)) 233 234 #endif /* _LINUX_SCHED_TASK_H */ 235