From: "Eric W. Biederman" In the last round of cleaning up the pid hash table a more general struct pid was introduced, that can be referenced counted. With the more general struct pid most if not all places where we store a pid_t we can now store a struct pid * and remove the need for a hash table lookup, and avoid any possible problems with pid roll over. Looking forward to the pid namespaces struct pid * gives us an absolute form a pid so we can compare and use them without caring which pid namespace we are in. This patchset introduces the infrastructure needed to use struct pid instead of pid_t, and then it goes on to convert two different kernel users that currently store a pid_t value. There are a lot more places to go but this is enough to get the basic idea. Before we can merge a pid namespace patch all of the kernel pid_t users need to be examined. Those that deal with user space processes need to be converted to using a struct pid *. Those that deal with kernel processes need to converted to using the kthread api. A rare few that only use their current processes pid values get to be left alone. This patch: task_session returns the struct pid of a tasks session. task_pgrp returns the struct pid of a tasks process group. task_tgid returns the struct pid of a tasks thread group. task_pid returns the struct pid of a tasks process id. These can be used to avoid unnecessary hash table lookups, and to implement safe pid comparisions in the face of a pid namespace. Signed-off-by: Eric W. Biederman Signed-off-by: Andrew Morton --- include/linux/sched.h | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff -puN include/linux/sched.h~pid-implement-access-helpers-for-a-tacks-various-process-groups include/linux/sched.h --- a/include/linux/sched.h~pid-implement-access-helpers-for-a-tacks-various-process-groups +++ a/include/linux/sched.h @@ -1020,6 +1020,26 @@ static inline pid_t process_group(struct return tsk->signal->pgrp; } +static inline struct pid *task_pid(struct task_struct *task) +{ + return task->pids[PIDTYPE_PID].pid; +} + +static inline struct pid *task_tgid(struct task_struct *task) +{ + return task->group_leader->pids[PIDTYPE_PID].pid; +} + +static inline struct pid *task_pgrp(struct task_struct *task) +{ + return task->group_leader->pids[PIDTYPE_PGID].pid; +} + +static inline struct pid *task_session(struct task_struct *task) +{ + return task->group_leader->pids[PIDTYPE_SID].pid; +} + /** * pid_alive - check that a task structure is not stale * @p: Task structure to be checked. _