9f57a54b6c
Now that I have changed all of the users remove the old version of these functions. This should be a clear hint to any out of tree users that they should use do_each_pid_task and while_each_pid_task for new code. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
120 lines
3.3 KiB
C
120 lines
3.3 KiB
C
#ifndef _LINUX_PID_H
|
|
#define _LINUX_PID_H
|
|
|
|
#include <linux/rcupdate.h>
|
|
|
|
enum pid_type
|
|
{
|
|
PIDTYPE_PID,
|
|
PIDTYPE_PGID,
|
|
PIDTYPE_SID,
|
|
PIDTYPE_MAX
|
|
};
|
|
|
|
/*
|
|
* What is struct pid?
|
|
*
|
|
* A struct pid is the kernel's internal notion of a process identifier.
|
|
* It refers to individual tasks, process groups, and sessions. While
|
|
* there are processes attached to it the struct pid lives in a hash
|
|
* table, so it and then the processes that it refers to can be found
|
|
* quickly from the numeric pid value. The attached processes may be
|
|
* quickly accessed by following pointers from struct pid.
|
|
*
|
|
* Storing pid_t values in the kernel and refering to them later has a
|
|
* problem. The process originally with that pid may have exited and the
|
|
* pid allocator wrapped, and another process could have come along
|
|
* and been assigned that pid.
|
|
*
|
|
* Referring to user space processes by holding a reference to struct
|
|
* task_struct has a problem. When the user space process exits
|
|
* the now useless task_struct is still kept. A task_struct plus a
|
|
* stack consumes around 10K of low kernel memory. More precisely
|
|
* this is THREAD_SIZE + sizeof(struct task_struct). By comparison
|
|
* a struct pid is about 64 bytes.
|
|
*
|
|
* Holding a reference to struct pid solves both of these problems.
|
|
* It is small so holding a reference does not consume a lot of
|
|
* resources, and since a new struct pid is allocated when the numeric pid
|
|
* value is reused (when pids wrap around) we don't mistakenly refer to new
|
|
* processes.
|
|
*/
|
|
|
|
struct pid
|
|
{
|
|
atomic_t count;
|
|
/* Try to keep pid_chain in the same cacheline as nr for find_pid */
|
|
int nr;
|
|
struct hlist_node pid_chain;
|
|
/* lists of tasks that use this pid */
|
|
struct hlist_head tasks[PIDTYPE_MAX];
|
|
struct rcu_head rcu;
|
|
};
|
|
|
|
struct pid_link
|
|
{
|
|
struct hlist_node node;
|
|
struct pid *pid;
|
|
};
|
|
|
|
static inline struct pid *get_pid(struct pid *pid)
|
|
{
|
|
if (pid)
|
|
atomic_inc(&pid->count);
|
|
return pid;
|
|
}
|
|
|
|
extern void FASTCALL(put_pid(struct pid *pid));
|
|
extern struct task_struct *FASTCALL(pid_task(struct pid *pid, enum pid_type));
|
|
extern struct task_struct *FASTCALL(get_pid_task(struct pid *pid,
|
|
enum pid_type));
|
|
|
|
extern struct pid *get_task_pid(struct task_struct *task, enum pid_type type);
|
|
|
|
/*
|
|
* attach_pid() and detach_pid() must be called with the tasklist_lock
|
|
* write-held.
|
|
*/
|
|
extern int FASTCALL(attach_pid(struct task_struct *task,
|
|
enum pid_type type, int nr));
|
|
|
|
extern void FASTCALL(detach_pid(struct task_struct *task, enum pid_type));
|
|
extern void FASTCALL(transfer_pid(struct task_struct *old,
|
|
struct task_struct *new, enum pid_type));
|
|
|
|
/*
|
|
* look up a PID in the hash table. Must be called with the tasklist_lock
|
|
* or rcu_read_lock() held.
|
|
*/
|
|
extern struct pid *FASTCALL(find_pid(int nr));
|
|
|
|
/*
|
|
* Lookup a PID in the hash table, and return with it's count elevated.
|
|
*/
|
|
extern struct pid *find_get_pid(int nr);
|
|
extern struct pid *find_ge_pid(int nr);
|
|
|
|
extern struct pid *alloc_pid(void);
|
|
extern void FASTCALL(free_pid(struct pid *pid));
|
|
|
|
static inline pid_t pid_nr(struct pid *pid)
|
|
{
|
|
pid_t nr = 0;
|
|
if (pid)
|
|
nr = pid->nr;
|
|
return nr;
|
|
}
|
|
|
|
#define do_each_pid_task(pid, type, task) \
|
|
do { \
|
|
struct hlist_node *pos___; \
|
|
if (pid != NULL) \
|
|
hlist_for_each_entry_rcu((task), pos___, \
|
|
&pid->tasks[type], pids[type].node) {
|
|
|
|
#define while_each_pid_task(pid, type, task) \
|
|
} \
|
|
} while (0)
|
|
|
|
#endif /* _LINUX_PID_H */
|