#ifndef _LINUX_PID_H
#define _LINUX_PID_H
-#include <linux/rcupdate.h>
-
enum pid_type
{
PIDTYPE_PID,
+ PIDTYPE_TGID,
PIDTYPE_PGID,
PIDTYPE_SID,
PIDTYPE_MAX,
PIDTYPE_REALPID
};
-/*
- * 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 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;
+ /* list of pids with the same nr, only one of them is in the hash */
+ struct list_head pid_list;
};
-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));
+#define pid_task(elem, type) \
+ list_entry(elem, struct task_struct, pids[type].pid_list)
/*
* 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 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));
/*
* 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.
+ * held.
*/
-extern struct pid *find_get_pid(int nr);
+extern struct pid *FASTCALL(find_pid(enum pid_type, int));
-extern struct pid *alloc_pid(void);
-extern void FASTCALL(free_pid(struct pid *pid));
+extern int alloc_pidmap(void);
+extern void FASTCALL(free_pidmap(int));
+extern void switch_exec_pids(struct task_struct *leader, struct task_struct *thread);
-#define pid_next(task, type) \
- ((task)->pids[(type)].node.next)
-
-#define pid_next_task(task, type) \
- hlist_entry(pid_next(task, type), struct task_struct, \
- pids[(type)].node)
-
-
-/* We could use hlist_for_each_entry_rcu here but it takes more arguments
- * than the do_each_task_pid/while_each_task_pid. So we roll our own
- * to preserve the existing interface.
- */
#define do_each_task_pid(who, type, task) \
if ((task = find_task_by_pid_type(type, who))) { \
- prefetch(pid_next(task, type)); \
+ prefetch((task)->pids[type].pid_list.next); \
do {
#define while_each_task_pid(who, type, task) \
- } while (pid_next(task, type) && ({ \
- task = pid_next_task(task, type); \
- rcu_dereference(task); \
- prefetch(pid_next(task, type)); \
- 1; }) ); \
- }
+ } while (task = pid_task((task)->pids[type].pid_list.next,\
+ type), \
+ prefetch((task)->pids[type].pid_list.next), \
+ hlist_unhashed(&(task)->pids[type].pid_chain)); \
+ } \
#endif /* _LINUX_PID_H */
git://git.onelab.eu / linux-2.6.git / blobdiff