[PATCH 1/1] ptrace: wait_task_zombie: s/->parent/->real_parent/

[PATCH 1/1] ptrace: wait_task_zombie: s/->parent/->real_parent/

[Oleg Nesterov]

Change wait_task_zombie() to use ->real_parent instead of ->parent.
We could even use current afaics, but ->real_parent is more clean.

We know that the child is not ptrace_reparented() and thus they are
equal. But we should avoid using task_struct->parent, we are going
to remove it.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>

--- PTRACE/kernel/exit.c~WAIT_NO_PARENT	2009-05-25 20:24:50.000000000 +0200
+++ PTRACE/kernel/exit.c	2009-05-25 21:47:24.000000000 +0200
@@ -1210,7 +1210,7 @@ static int wait_task_zombie(struct wait_
 		 * p->signal fields, because they are only touched by
 		 * __exit_signal, which runs with tasklist_lock
 		 * write-locked anyway, and so is excluded here.  We do
-		 * need to protect the access to p->parent->signal fields,
+		 * need to protect the access to parent->signal fields,
 		 * as other threads in the parent group can be right
 		 * here reaping other children at the same time.
 		 *
@@ -1219,8 +1219,8 @@ static int wait_task_zombie(struct wait_
 		 * group including the group leader.
 		 */
 		thread_group_cputime(p, &cputime);
-		spin_lock_irq(&p->parent->sighand->siglock);
-		psig = p->parent->signal;
+		spin_lock_irq(&p->real_parent->sighand->siglock);
+		psig = p->real_parent->signal;
 		sig = p->signal;
 		psig->cutime =
 			cputime_add(psig->cutime,
@@ -1251,7 +1251,7 @@ static int wait_task_zombie(struct wait_
 			sig->oublock + sig->coublock;
 		task_io_accounting_add(&psig->ioac, &p->ioac);
 		task_io_accounting_add(&psig->ioac, &sig->ioac);
-		spin_unlock_irq(&p->parent->sighand->siglock);
+		spin_unlock_irq(&p->real_parent->sighand->siglock);
 	}
 
 	/*

Re: [PATCH 1/1] ptrace: wait_task_zombie: s/->parent/->real_parent/

[Roland McGrath]

> Change wait_task_zombie() to use ->real_parent instead of ->parent.

Acked-by: Roland McGrath <roland@redhat.com>

> We could even use current afaics, but ->real_parent is more clean.

Indeed, though the caller might not be ->real_parent, it will always be
one that shares ->signal with ->real_parent.  But I agree that using
->real_parent is the clean way.  Incidentally, as readability cleanup it
would make a lot of sense to move that block into a subroutine.


Thanks,
Roland