pid: Implement PIDTYPE_TGID
Everywhere except in the pid array we distinguish between a tasks pid and
a tasks tgid (thread group id). Even in the enumeration we want that
distinction sometimes so we have added __PIDTYPE_TGID. With leader_pid
we almost have an implementation of PIDTYPE_TGID in struct signal_struct.
Add PIDTYPE_TGID as a first class member of the pid_type enumeration and
into the pids array. Then remove the __PIDTYPE_TGID special case and the
leader_pid in signal_struct.
The net size increase is just an extra pointer added to struct pid and
an extra pair of pointers of an hlist_node added to task_struct.
The effect on code maintenance is the removal of a number of special
cases today and the potential to remove many more special cases as
PIDTYPE_TGID gets used to it's fullest. The long term potential
is allowing zombie thread group leaders to exit, which will remove
a lot more special cases in the code.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
diff --git a/kernel/exit.c b/kernel/exit.c
index 1643242..25582b4 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -73,6 +73,7 @@ static void __unhash_process(struct task_struct *p, bool group_dead)
nr_threads--;
detach_pid(p, PIDTYPE_PID);
if (group_dead) {
+ detach_pid(p, PIDTYPE_TGID);
detach_pid(p, PIDTYPE_PGID);
detach_pid(p, PIDTYPE_SID);
