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Commit 087806b1 authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

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: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarTejun Heo <tj@kernel.org>
parent d4f7c511

fs/exec.c

+1 −0
Original line number Diff line number Diff line
@@ -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;

include/linux/sched.h

+4 −2
Original line number Diff line number Diff line
@@ -2284,8 +2284,10 @@ static inline int get_nr_threads(struct task_struct *tsk) 
	return tsk->signal->nr_threads;

}



/* de_thread depends on thread_group_leader not being a pid based check */

#define thread_group_leader(p)	(p == p->group_leader)

static inline bool thread_group_leader(struct task_struct *p)

{

	return p->exit_signal >= 0;

}



/* Do to the insanities of de_thread it is possible for a process

 * to have the pid of the thread group leader without actually being