Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | #ifndef _LINUX_PID_H |
| 2 | #define _LINUX_PID_H |
| 3 | |
Eric W. Biederman | 92476d7 | 2006-03-31 02:31:42 -0800 | [diff] [blame] | 4 | #include <linux/rcupdate.h> |
| 5 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6 | enum pid_type |
| 7 | { |
| 8 | PIDTYPE_PID, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 9 | PIDTYPE_PGID, |
| 10 | PIDTYPE_SID, |
| 11 | PIDTYPE_MAX |
| 12 | }; |
| 13 | |
Eric W. Biederman | 92476d7 | 2006-03-31 02:31:42 -0800 | [diff] [blame] | 14 | /* |
| 15 | * What is struct pid? |
| 16 | * |
| 17 | * A struct pid is the kernel's internal notion of a process identifier. |
| 18 | * It refers to individual tasks, process groups, and sessions. While |
| 19 | * there are processes attached to it the struct pid lives in a hash |
| 20 | * table, so it and then the processes that it refers to can be found |
| 21 | * quickly from the numeric pid value. The attached processes may be |
| 22 | * quickly accessed by following pointers from struct pid. |
| 23 | * |
| 24 | * Storing pid_t values in the kernel and refering to them later has a |
| 25 | * problem. The process originally with that pid may have exited and the |
| 26 | * pid allocator wrapped, and another process could have come along |
| 27 | * and been assigned that pid. |
| 28 | * |
| 29 | * Referring to user space processes by holding a reference to struct |
| 30 | * task_struct has a problem. When the user space process exits |
| 31 | * the now useless task_struct is still kept. A task_struct plus a |
| 32 | * stack consumes around 10K of low kernel memory. More precisely |
| 33 | * this is THREAD_SIZE + sizeof(struct task_struct). By comparison |
| 34 | * a struct pid is about 64 bytes. |
| 35 | * |
| 36 | * Holding a reference to struct pid solves both of these problems. |
| 37 | * It is small so holding a reference does not consume a lot of |
Sukadev Bhattiprolu | 84d7378 | 2006-12-08 02:38:01 -0800 | [diff] [blame] | 38 | * resources, and since a new struct pid is allocated when the numeric pid |
| 39 | * value is reused (when pids wrap around) we don't mistakenly refer to new |
| 40 | * processes. |
Eric W. Biederman | 92476d7 | 2006-03-31 02:31:42 -0800 | [diff] [blame] | 41 | */ |
| 42 | |
Sukadev Bhattiprolu | 4c3f2ea | 2007-10-18 23:40:03 -0700 | [diff] [blame] | 43 | |
| 44 | /* |
| 45 | * struct upid is used to get the id of the struct pid, as it is |
| 46 | * seen in particular namespace. Later the struct pid is found with |
| 47 | * find_pid_ns() using the int nr and struct pid_namespace *ns. |
| 48 | */ |
| 49 | |
| 50 | struct upid { |
| 51 | /* Try to keep pid_chain in the same cacheline as nr for find_pid */ |
| 52 | int nr; |
| 53 | struct pid_namespace *ns; |
| 54 | struct hlist_node pid_chain; |
| 55 | }; |
| 56 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 57 | struct pid |
| 58 | { |
Eric W. Biederman | 92476d7 | 2006-03-31 02:31:42 -0800 | [diff] [blame] | 59 | atomic_t count; |
Eric W. Biederman | 92476d7 | 2006-03-31 02:31:42 -0800 | [diff] [blame] | 60 | /* lists of tasks that use this pid */ |
| 61 | struct hlist_head tasks[PIDTYPE_MAX]; |
| 62 | struct rcu_head rcu; |
Pavel Emelyanov | caafa43 | 2008-04-30 00:54:31 -0700 | [diff] [blame] | 63 | unsigned int level; |
Sukadev Bhattiprolu | 4c3f2ea | 2007-10-18 23:40:03 -0700 | [diff] [blame] | 64 | struct upid numbers[1]; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 65 | }; |
| 66 | |
Sukadev Bhattiprolu | 820e45d | 2007-05-10 22:23:00 -0700 | [diff] [blame] | 67 | extern struct pid init_struct_pid; |
| 68 | |
Eric W. Biederman | 92476d7 | 2006-03-31 02:31:42 -0800 | [diff] [blame] | 69 | struct pid_link |
| 70 | { |
| 71 | struct hlist_node node; |
| 72 | struct pid *pid; |
| 73 | }; |
| 74 | |
| 75 | static inline struct pid *get_pid(struct pid *pid) |
| 76 | { |
| 77 | if (pid) |
| 78 | atomic_inc(&pid->count); |
| 79 | return pid; |
| 80 | } |
| 81 | |
Harvey Harrison | b3c9752 | 2008-02-13 15:03:15 -0800 | [diff] [blame] | 82 | extern void put_pid(struct pid *pid); |
| 83 | extern struct task_struct *pid_task(struct pid *pid, enum pid_type); |
| 84 | extern struct task_struct *get_pid_task(struct pid *pid, enum pid_type); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 85 | |
Oleg Nesterov | 1a657f78 | 2006-10-02 02:18:59 -0700 | [diff] [blame] | 86 | extern struct pid *get_task_pid(struct task_struct *task, enum pid_type type); |
| 87 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 88 | /* |
| 89 | * attach_pid() and detach_pid() must be called with the tasklist_lock |
| 90 | * write-held. |
| 91 | */ |
Oleg Nesterov | 24336ea | 2008-04-30 00:54:26 -0700 | [diff] [blame] | 92 | extern void attach_pid(struct task_struct *task, enum pid_type type, |
| 93 | struct pid *pid); |
Harvey Harrison | b3c9752 | 2008-02-13 15:03:15 -0800 | [diff] [blame] | 94 | extern void detach_pid(struct task_struct *task, enum pid_type); |
Oleg Nesterov | 24336ea | 2008-04-30 00:54:26 -0700 | [diff] [blame] | 95 | extern void change_pid(struct task_struct *task, enum pid_type, |
| 96 | struct pid *pid); |
Harvey Harrison | b3c9752 | 2008-02-13 15:03:15 -0800 | [diff] [blame] | 97 | extern void transfer_pid(struct task_struct *old, struct task_struct *new, |
| 98 | enum pid_type); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 99 | |
Pavel Emelyanov | 198fe21 | 2007-10-18 23:40:06 -0700 | [diff] [blame] | 100 | struct pid_namespace; |
| 101 | extern struct pid_namespace init_pid_ns; |
| 102 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 103 | /* |
| 104 | * look up a PID in the hash table. Must be called with the tasklist_lock |
Eric W. Biederman | 92476d7 | 2006-03-31 02:31:42 -0800 | [diff] [blame] | 105 | * or rcu_read_lock() held. |
Pavel Emelyanov | 198fe21 | 2007-10-18 23:40:06 -0700 | [diff] [blame] | 106 | * |
| 107 | * find_pid_ns() finds the pid in the namespace specified |
| 108 | * find_pid() find the pid by its global id, i.e. in the init namespace |
| 109 | * find_vpid() finr the pid by its virtual id, i.e. in the current namespace |
| 110 | * |
| 111 | * see also find_task_by_pid() set in include/linux/sched.h |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 112 | */ |
Harvey Harrison | b3c9752 | 2008-02-13 15:03:15 -0800 | [diff] [blame] | 113 | extern struct pid *find_pid_ns(int nr, struct pid_namespace *ns); |
Pavel Emelyanov | 8990571 | 2007-10-18 23:40:19 -0700 | [diff] [blame] | 114 | extern struct pid *find_vpid(int nr); |
| 115 | extern struct pid *find_pid(int nr); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 116 | |
Eric W. Biederman | 92476d7 | 2006-03-31 02:31:42 -0800 | [diff] [blame] | 117 | /* |
| 118 | * Lookup a PID in the hash table, and return with it's count elevated. |
| 119 | */ |
| 120 | extern struct pid *find_get_pid(int nr); |
Pavel Emelyanov | 198fe21 | 2007-10-18 23:40:06 -0700 | [diff] [blame] | 121 | extern struct pid *find_ge_pid(int nr, struct pid_namespace *); |
Pavel Emelyanov | 74bd59b | 2008-02-08 04:18:24 -0800 | [diff] [blame] | 122 | int next_pidmap(struct pid_namespace *pid_ns, int last); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 123 | |
Pavel Emelyanov | 8ef047a | 2007-10-18 23:40:05 -0700 | [diff] [blame] | 124 | extern struct pid *alloc_pid(struct pid_namespace *ns); |
Harvey Harrison | b3c9752 | 2008-02-13 15:03:15 -0800 | [diff] [blame] | 125 | extern void free_pid(struct pid *pid); |
Eric W. Biederman | 92476d7 | 2006-03-31 02:31:42 -0800 | [diff] [blame] | 126 | |
Pavel Emelyanov | 7af5729 | 2007-10-18 23:40:06 -0700 | [diff] [blame] | 127 | /* |
| 128 | * the helpers to get the pid's id seen from different namespaces |
| 129 | * |
| 130 | * pid_nr() : global id, i.e. the id seen from the init namespace; |
Eric W. Biederman | 44c4e1b | 2008-02-08 04:19:15 -0800 | [diff] [blame] | 131 | * pid_vnr() : virtual id, i.e. the id seen from the pid namespace of |
| 132 | * current. |
Pavel Emelyanov | 7af5729 | 2007-10-18 23:40:06 -0700 | [diff] [blame] | 133 | * pid_nr_ns() : id seen from the ns specified. |
| 134 | * |
| 135 | * see also task_xid_nr() etc in include/linux/sched.h |
| 136 | */ |
| 137 | |
Eric W. Biederman | 5feb8f5 | 2006-10-02 02:17:12 -0700 | [diff] [blame] | 138 | static inline pid_t pid_nr(struct pid *pid) |
| 139 | { |
| 140 | pid_t nr = 0; |
| 141 | if (pid) |
Pavel Emelyanov | 7af5729 | 2007-10-18 23:40:06 -0700 | [diff] [blame] | 142 | nr = pid->numbers[0].nr; |
| 143 | return nr; |
| 144 | } |
| 145 | |
| 146 | pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns); |
Eric W. Biederman | 44c4e1b | 2008-02-08 04:19:15 -0800 | [diff] [blame] | 147 | pid_t pid_vnr(struct pid *pid); |
Eric W. Biederman | 5feb8f5 | 2006-10-02 02:17:12 -0700 | [diff] [blame] | 148 | |
Andrew Morton | 1d32849 | 2006-10-03 01:13:45 -0700 | [diff] [blame] | 149 | #define do_each_pid_task(pid, type, task) \ |
| 150 | do { \ |
| 151 | struct hlist_node *pos___; \ |
| 152 | if (pid != NULL) \ |
| 153 | hlist_for_each_entry_rcu((task), pos___, \ |
Oleg Nesterov | d387cae | 2006-10-02 02:17:22 -0700 | [diff] [blame] | 154 | &pid->tasks[type], pids[type].node) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 155 | |
Oleg Nesterov | 46f382d | 2008-02-08 04:19:19 -0800 | [diff] [blame] | 156 | /* |
| 157 | * Both old and new leaders may be attached to |
| 158 | * the same pid in the middle of de_thread(). |
| 159 | */ |
Andrew Morton | 1d32849 | 2006-10-03 01:13:45 -0700 | [diff] [blame] | 160 | #define while_each_pid_task(pid, type, task) \ |
Oleg Nesterov | 46f382d | 2008-02-08 04:19:19 -0800 | [diff] [blame] | 161 | if (type == PIDTYPE_PID) \ |
| 162 | break; \ |
Andrew Morton | 1d32849 | 2006-10-03 01:13:45 -0700 | [diff] [blame] | 163 | } \ |
Oleg Nesterov | d387cae | 2006-10-02 02:17:22 -0700 | [diff] [blame] | 164 | } while (0) |
Eric W. Biederman | 558cb32 | 2006-10-02 02:17:09 -0700 | [diff] [blame] | 165 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 166 | #endif /* _LINUX_PID_H */ |