redefine thread_group_leader() as exit_signal >= 0

Change de_thread() to set old_leader->exit_signal = -1. This is
good for the consistency, it is no longer the leader and all
sub-threads have exit_signal = -1 set by copy_process(CLONE_THREAD).

And this allows us to micro-optimize thread_group_leader(), it can
simply check exit_signal >= 0. This also makes sense because we
should move ->group_leader from task_struct to signal_struct.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Tejun Heo <tj@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/exec.c b/fs/exec.c
index 8dca45b0dae8..c3d517bfdd27 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -963,6 +963,7 @@ static int de_thread(struct task_struct *tsk)
                 leader->group_leader = tsk;
 
                 tsk->exit_signal = SIGCHLD;
+                leader->exit_signal = -1;
 
                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
                 leader->exit_state = EXIT_DEAD;