include/linux/pid.h

13  * What is struct pid?
15  * A struct pid is the kernel's internal notion of a process identifier.
17  * there are processes attached to it the struct pid lives in a hash
19  * quickly from the numeric pid value.  The attached processes may be
20  * quickly accessed by following pointers from struct pid.
23  * problem.  The process originally with that pid may have exited and the
24  * pid allocator wrapped, and another process could have come along
25  * and been assigned that pid.
32  * a struct pid is about 64 bytes.
34  * Holding a reference to struct pid solves both of these problems.
36  * resources, and since a new struct pid is allocated when the numeric pid
43  * struct upid is used to get the id of the struct pid, as it is
44  * seen in particular namespace. Later the struct pid is found with
55 struct pid
62 	/* lists of tasks that use this pid */
71 extern struct pid init_struct_pid;
75 struct pid *pidfd_pid(const struct file *file);
76 struct pid *pidfd_get_pid(unsigned int fd, unsigned int *flags);
78 int pidfd_prepare(struct pid *pid, unsigned int flags, struct file **ret);
81 static inline struct pid *get_pid(struct pid *pid)
83 	if (pid)
84 		refcount_inc(&pid->count);
85 	return pid;
88 extern void put_pid(struct pid *pid);
89 extern struct task_struct *pid_task(struct pid *pid, enum pid_type);
90 static inline bool pid_has_task(struct pid *pid, enum pid_type type)
92 	return !hlist_empty(&pid->tasks[type]);
94 extern struct task_struct *get_pid_task(struct pid *pid, enum pid_type);
96 extern struct pid *get_task_pid(struct task_struct *task, enum pid_type type);
104 			struct pid *pid);
116  * find_pid_ns() finds the pid in the namespace specified
117  * find_vpid() finds the pid by its virtual id, i.e. in the current namespace
121 extern struct pid *find_pid_ns(int nr, struct pid_namespace *ns);
122 extern struct pid *find_vpid(int nr);
127 extern struct pid *find_get_pid(int nr);
128 extern struct pid *find_ge_pid(int nr, struct pid_namespace *);
130 extern struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
132 extern void free_pid(struct pid *pid);
136  * ns_of_pid() returns the pid namespace in which the specified pid was
141  * 	an attached 'struct pid' (see attach_pid(), detach_pid()) i.e @pid
142  * 	is expected to be non-NULL. If @pid is NULL, caller should handle
143  * 	the resulting NULL pid-ns.
145 static inline struct pid_namespace *ns_of_pid(struct pid *pid)
148 	if (pid)
149 		ns = pid->numbers[pid->level].ns;
154  * is_child_reaper returns true if the pid is the init process
157  * with the pid number.
159 static inline bool is_child_reaper(struct pid *pid)
161 	return pid->numbers[pid->level].nr == 1;
165  * the helpers to get the pid's id seen from different namespaces
168  * pid_vnr()   : virtual id, i.e. the id seen from the pid namespace of
175 static inline pid_t pid_nr(struct pid *pid)
178 	if (pid)
179 		nr = pid->numbers[0].nr;
183 pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns);
184 pid_t pid_vnr(struct pid *pid);
186 #define do_each_pid_task(pid, type, task)				\
188 		if ((pid) != NULL)					\
190 				&(pid)->tasks[type], pid_links[type]) {
194 			 * the same pid in the middle of de_thread().
196 #define while_each_pid_task(pid, type, task)				\
202 #define do_each_pid_thread(pid, type, task)				\
203 	do_each_pid_task(pid, type, task) {				\
207 #define while_each_pid_thread(pid, type, task)				\
210 	} while_each_pid_task(pid, type, task)
212 static inline struct pid *task_pid(struct task_struct *task)
222  * task_xid_vnr()    : virtual id, i.e. the id seen from the pid namespace of
226  * see also pid_nr() etc in include/linux/pid.h
232 	return tsk->pid;
299 	pid_t pid = 0;
303 		pid = task_tgid_nr_ns(rcu_dereference(tsk->real_parent), ns);
306 	return pid;