forget_original_parent: split out the un-ptrace part

By discussion with Roland.

- Rename ptrace_exit() to exit_ptrace(), and change it to do all the
  necessary work with ->ptraced list by its own.

- Move this code from exit.c to ptrace.c

- Update the comment in ptrace_detach() to explain the rechecking of
  the child->ptrace.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Metzger, Markus T" <markus.t.metzger@intel.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 6 insertions, 1 deletions

diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 1a2b0cb55535..67c15653fc23 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -94,7 +94,7 @@ extern void ptrace_notify(int exit_code);
 extern void __ptrace_link(struct task_struct *child,
                           struct task_struct *new_parent);
 extern void __ptrace_unlink(struct task_struct *child);
-extern int __ptrace_detach(struct task_struct *tracer, struct task_struct *p);
+extern void exit_ptrace(struct task_struct *tracer);
 extern void ptrace_fork(struct task_struct *task, unsigned long clone_flags);
 #define PTRACE_MODE_READ   1
 #define PTRACE_MODE_ATTACH 2
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9186f8c5d5f2..b47c94e7560b 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2061,6 +2061,11 @@ static inline int thread_group_empty(struct task_struct *p)
 #define delay_group_leader(p) \
                 (thread_group_leader(p) && !thread_group_empty(p))
 
+static inline int task_detached(struct task_struct *p)
+{
+        return p->exit_signal == -1;
+}
+
 /*
  * Protects ->fs, ->files, ->mm, ->group_info, ->comm, keyring
  * subscriptions and synchronises with wait4().  Also used in procfs.  Also