redefine thread_group_leader() as exit_signal >= 0 (087806b1) · Commits · 戴 / test

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>

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

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