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Subjectrfc, leader_pid_type()
Eric, Pavel.

Without tasklist lock held, task_tgid/task_pgrp/task_session can return the
bogus NULL. Note that the last 2 can return NULL even if task == current.

What do you think if we add yet another helper?

struct pid *leader_pid_type(struct task_struct *task, enum pid_type type)
{
struct pid *ret;
retry:
ret = task->group_leader->pids[type].pid;
if (likely(ret != NULL) || !pid_alive(task))
return ret;
/*
* We hit the old leader in the middle of de_thread(),
* or setsid/setpgrp is in progress.
*/
cpu_relax();
goto retry;
}
Yes, we already have a lot helpers... The one potential user is
check_kill_permission(), but it can live without it.

What do you think, do you see other possible users? Say, do_task_stat() may
report sid = 0, but this is minor of course...

Oleg.



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