Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932562AbWCHUB4 (ORCPT ); Wed, 8 Mar 2006 15:01:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932563AbWCHUB4 (ORCPT ); Wed, 8 Mar 2006 15:01:56 -0500 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:46057 "EHLO ebiederm.dsl.xmission.com") by vger.kernel.org with ESMTP id S932562AbWCHUBz (ORCPT ); Wed, 8 Mar 2006 15:01:55 -0500 To: Oleg Nesterov Cc: Andrew Morton , linux-kernel@vger.kernel.org, Ingo Molnar , "Paul E. McKenney" , Linus Torvalds Subject: Re: [PATCH rc5-mm] pids: kill PIDTYPE_TGID References: <440DEADB.72C3A8A6@tv-sign.ru> <440EED04.57FF5594@tv-sign.ru> <440F2F4A.3E91C272@tv-sign.ru> From: ebiederm@xmission.com (Eric W. Biederman) Date: Wed, 08 Mar 2006 13:00:58 -0700 In-Reply-To: <440F2F4A.3E91C272@tv-sign.ru> (Oleg Nesterov's message of "Wed, 08 Mar 2006 22:23:54 +0300") Message-ID: User-Agent: Gnus/5.1007 (Gnus v5.10.7) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2256 Lines: 69 Oleg Nesterov 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++; > } Eric - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/