include/linux/sched/task.h

   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 static inline struct task_struct *tryget_task_struct(struct task_struct *t)
 124 {
 125         return refcount_inc_not_zero(&t->usage) ? t : NULL;
 126 }
 127
 128 extern void __put_task_struct(struct task_struct *t);
 129 extern void __put_task_struct_rcu_cb(struct rcu_head *rhp);
 130
 131 static inline void put_task_struct(struct task_struct *t)
 132 {
 133         if (!refcount_dec_and_test(&t->usage))
 134                 return;
 135
 136         /*
 137          * In !RT, it is always safe to call __put_task_struct().
 138          * Under RT, we can only call it in preemptible context.
 139          */
 140         if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible()) {
 141                 static DEFINE_WAIT_OVERRIDE_MAP(put_task_map, LD_WAIT_SLEEP);
 142
 143                 lock_map_acquire_try(&put_task_map);
 144                 __put_task_struct(t);
 145                 lock_map_release(&put_task_map);
 146                 return;
 147         }
 148
 149         /*
 150          * under PREEMPT_RT, we can't call put_task_struct
 151          * in atomic context because it will indirectly
 152          * acquire sleeping locks.
 153          *
 154          * call_rcu() will schedule delayed_put_task_struct_rcu()
 155          * to be called in process context.
 156          *
 157          * __put_task_struct() is called when
 158          * refcount_dec_and_test(&t->usage) succeeds.
 159          *
 160          * This means that it can't "conflict" with
 161          * put_task_struct_rcu_user() which abuses ->rcu the same
 162          * way; rcu_users has a reference so task->usage can't be
 163          * zero after rcu_users 1 -> 0 transition.
 164          *
 165          * delayed_free_task() also uses ->rcu, but it is only called
 166          * when it fails to fork a process. Therefore, there is no
 167          * way it can conflict with put_task_struct().
 168          */
 169         call_rcu(&t->rcu, __put_task_struct_rcu_cb);
 170 }
 171
 172 DEFINE_FREE(put_task, struct task_struct *, if (_T) put_task_struct(_T))
 173
 174 static inline void put_task_struct_many(struct task_struct *t, int nr)
 175 {
 176         if (refcount_sub_and_test(nr, &t->usage))
 177                 __put_task_struct(t);
 178 }
 179
 180 void put_task_struct_rcu_user(struct task_struct *task);
 181
 182 /* Free all architecture-specific resources held by a thread. */
 183 void release_thread(struct task_struct *dead_task);
 184
 185 #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT
 186 extern int arch_task_struct_size __read_mostly;
 187 #else
 188 # define arch_task_struct_size (sizeof(struct task_struct))
 189 #endif
 190
 191 #ifndef CONFIG_HAVE_ARCH_THREAD_STRUCT_WHITELIST
 192 /*
 193  * If an architecture has not declared a thread_struct whitelist we
 194  * must assume something there may need to be copied to userspace.
 195  */
 196 static inline void arch_thread_struct_whitelist(unsigned long *offset,
 197                                                 unsigned long *size)
 198 {
 199         *offset = 0;
 200         /* Handle dynamically sized thread_struct. */
 201         *size = arch_task_struct_size - offsetof(struct task_struct, thread);
 202 }
 203 #endif
 204
 205 #ifdef CONFIG_VMAP_STACK
 206 static inline struct vm_struct *task_stack_vm_area(const struct task_struct *t)
 207 {
 208         return t->stack_vm_area;
 209 }
 210 #else
 211 static inline struct vm_struct *task_stack_vm_area(const struct task_struct *t)
 212 {
 213         return NULL;
 214 }
 215 #endif
 216
 217 /*
 218  * Protects ->fs, ->files, ->mm, ->group_info, ->comm, keyring
 219  * subscriptions and synchronises with wait4().  Also used in procfs.  Also
 220  * pins the final release of task.io_context.  Also protects ->cpuset and
 221  * ->cgroup.subsys[]. And ->vfork_done. And ->sysvshm.shm_clist.
 222  *
 223  * Nests both inside and outside of read_lock(&tasklist_lock).
 224  * It must not be nested with write_lock_irq(&tasklist_lock),
 225  * neither inside nor outside.
 226  */
 227 static inline void task_lock(struct task_struct *p)
 228 {
 229         spin_lock(&p->alloc_lock);
 230 }
 231
 232 static inline void task_unlock(struct task_struct *p)
 233 {
 234         spin_unlock(&p->alloc_lock);
 235 }
 236
 237 DEFINE_GUARD(task_lock, struct task_struct *, task_lock(_T), task_unlock(_T))
 238
 239 #endif /* _LINUX_SCHED_TASK_H */