Messages in this thread | | | Subject | Re: [PATCH rc5-mm] pids: kill PIDTYPE_TGID | From | (Eric W. Biederman) | Date | Wed, 08 Mar 2006 13:00:58 -0700 |
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Oleg Nesterov <oleg@tv-sign.ru> writes:
> Changes: > s/tgrp/thread_group/ > > make it rcu-safe > > [PATCH rc5-mm] pids: kill PIDTYPE_TGID > > depends on pidhash-dont-count-idle-threads.patch > > This patch kills PIDTYPE_TGID pid_type thus saving one hash table > in kernel/pid.c and speeding up subthreads create/destroy a bit. > It is also a preparation for the further tref/pids rework. > > This patch adds 'struct list_head thread_group' to 'struct task_struct' > instead. > > We don't detach group leader from PIDTYPE_PID namespace until another > thread inherits it's ->pid == ->tgid, so we are safe wrt premature > free_pidmap(->tgid) call. > > Currently there are no users of find_task_by_pid_type(PIDTYPE_TGID). > Should the need arise, we can use find_task_by_pid()->group_leader.
Looks good. I have one final nit.
> --- 2.6.16-rc5/kernel/fork.c~1_TGID 2006-03-09 00:17:24.000000000 +0300 > +++ 2.6.16-rc5/kernel/fork.c 2006-03-09 00:41:35.000000000 +0300 > @@ -1100,6 +1100,7 @@ static task_t *copy_process(unsigned lon > * We dont wake it up yet. > */ > p->group_leader = p; > + INIT_LIST_HEAD(&p->thread_group); > INIT_LIST_HEAD(&p->ptrace_children); > INIT_LIST_HEAD(&p->ptrace_list); > > @@ -1153,7 +1154,9 @@ static task_t *copy_process(unsigned lon > retval = -EAGAIN; > goto bad_fork_cleanup_namespace; > } > + > p->group_leader = current->group_leader; > + list_add_tail_rcu(&p->thread_group, ¤t->thread_group); Can this be: list_add_tail_rcu(&p->thread_group, ¤t->group_leader->thread_group);
That way at least the odds of missing a new task_struct when doing an rcu traversal are reduced almost to 0.
> > if (current->signal->group_stop_count > 0) { > /* > @@ -1201,7 +1204,6 @@ static task_t *copy_process(unsigned lon > list_add_tail(&p->tasks, &init_task.tasks); > __get_cpu_var(process_counts)++; > } > - attach_pid(p, PIDTYPE_TGID, p->tgid); > attach_pid(p, PIDTYPE_PID, p->pid); > nr_threads++; > }
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