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redefine thread_group_leader() as exit_signal >= 0

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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>
This commit is contained in:
Oleg Nesterov 2011-06-22 23:10:26 +02:00
parent d4f7c511c1
commit 087806b128
2 changed files with 5 additions and 2 deletions
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1
fs/exec.c
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@ -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;

6
include/linux/sched.h
View File

@ -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