Isolate some explicit usage of task->tgid

With pid namespaces this field is now dangerous to use explicitly, so hide
it behind the helpers.

Also the pid and pgrp fields o task_struct and signal_struct are to be
deprecated.  Unfortunately this patch cannot be sent right now as this
leads to tons of warnings, so start isolating them, and deprecate later.

Actually the p->tgid == pid has to be changed to has_group_leader_pid(),
but Oleg pointed out that in case of posix cpu timers this is the same, and
thread_group_leader() is more preferable.

Signed-off-by: Pavel Emelyanov <[email protected]>
Acked-by: Oleg Nesterov <[email protected]>
Cc: Sukadev Bhattiprolu <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index f4d969e85612..eb2ae68804aa 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1725,6 +1725,12 @@ static inline int has_group_leader_pid(struct task_struct *p)
 	return p->pid == p->tgid;
 }
 
+static inline
+int same_thread_group(struct task_struct *p1, struct task_struct *p2)
+{
+	return p1->tgid == p2->tgid;
+}
+
 static inline struct task_struct *next_thread(const struct task_struct *p)
 {
 	return list_entry(rcu_dereference(p->thread_group.next),