From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932560Ab0CXRvi (ORCPT ); Wed, 24 Mar 2010 13:51:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41939 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932327Ab0CXRvh (ORCPT ); Wed, 24 Mar 2010 13:51:37 -0400 Date: Wed, 24 Mar 2010 18:49:36 +0100 From: Oleg Nesterov To: Andrew Morton Cc: Alexey Dobriyan , "Eric W. Biederman" , Roland McGrath , linux-kernel@vger.kernel.org Subject: [PATCH -mm 1/1] proc: turn signal_struct->count into "int nr_threads" Message-ID: <20100324174936.GA21534@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org No functional changes, just s/atomic_t count/int nr_threads/. With the recent changes this counter has a single user, get_nr_threads() And, none of its callers need the really accurate number of threads, not to mention each caller obviously races with fork/exit. It is only used to report this value to the user-space, except first_tid() uses it to avoid the unnecessary while_each_thread() loop in the unlikely case. It is a bit sad we need a word in struct signal_struct for this, perhaps we can change get_nr_threads() to approximate the number of threads using signal->live and kill ->nr_threads later. Signed-off-by: Oleg Nesterov --- include/linux/sched.h | 4 ++-- include/linux/init_task.h | 2 +- kernel/exit.c | 5 +---- kernel/fork.c | 8 ++++---- 4 files changed, 8 insertions(+), 11 deletions(-) --- 34-rc1/include/linux/sched.h~14_S_COUNT_NR_THREADS 2010-03-24 17:35:30.000000000 +0100 +++ 34-rc1/include/linux/sched.h 2010-03-24 18:07:03.000000000 +0100 @@ -518,8 +518,8 @@ struct thread_group_cputimer { */ struct signal_struct { atomic_t sigcnt; - atomic_t count; atomic_t live; + int nr_threads; wait_queue_head_t wait_chldexit; /* for wait4() */ @@ -2150,7 +2150,7 @@ extern bool current_is_single_threaded(v static inline int get_nr_threads(struct task_struct *tsk) { - return atomic_read(&tsk->signal->count); + return tsk->signal->nr_threads; } /* de_thread depends on thread_group_leader not being a pid based check */ --- 34-rc1/include/linux/init_task.h~14_S_COUNT_NR_THREADS 2010-03-24 17:35:30.000000000 +0100 +++ 34-rc1/include/linux/init_task.h 2010-03-24 18:07:03.000000000 +0100 @@ -16,7 +16,7 @@ extern struct files_struct init_files; extern struct fs_struct init_fs; #define INIT_SIGNALS(sig) { \ - .count = ATOMIC_INIT(1), \ + .nr_threads = 1, \ .wait_chldexit = __WAIT_QUEUE_HEAD_INITIALIZER(sig.wait_chldexit),\ .shared_pending = { \ .list = LIST_HEAD_INIT(sig.shared_pending.list), \ --- 34-rc1/kernel/exit.c~14_S_COUNT_NR_THREADS 2010-03-24 17:36:32.000000000 +0100 +++ 34-rc1/kernel/exit.c 2010-03-24 18:08:14.000000000 +0100 @@ -84,14 +84,10 @@ static void __exit_signal(struct task_st struct sighand_struct *sighand; struct tty_struct *uninitialized_var(tty); - BUG_ON(!sig); - BUG_ON(!atomic_read(&sig->count)); - sighand = rcu_dereference_check(tsk->sighand, rcu_read_lock_held() || lockdep_is_held(&tasklist_lock)); spin_lock(&sighand->siglock); - atomic_dec(&sig->count); posix_cpu_timers_exit(tsk); if (group_dead) { @@ -131,6 +127,7 @@ static void __exit_signal(struct task_st sig->sum_sched_runtime += tsk->se.sum_exec_runtime; } + sig->nr_threads--; __unhash_process(tsk, group_dead); /* --- 34-rc1/kernel/fork.c~14_S_COUNT_NR_THREADS 2010-03-24 17:35:30.000000000 +0100 +++ 34-rc1/kernel/fork.c 2010-03-24 18:07:03.000000000 +0100 @@ -881,9 +881,9 @@ static int copy_signal(unsigned long clo if (!sig) return -ENOMEM; - atomic_set(&sig->sigcnt, 1); - atomic_set(&sig->count, 1); + sig->nr_threads = 1; atomic_set(&sig->live, 1); + atomic_set(&sig->sigcnt, 1); init_waitqueue_head(&sig->wait_chldexit); if (clone_flags & CLONE_NEWPID) sig->flags |= SIGNAL_UNKILLABLE; @@ -1257,9 +1257,9 @@ static struct task_struct *copy_process( } if (clone_flags & CLONE_THREAD) { - atomic_inc(¤t->signal->sigcnt); - atomic_inc(¤t->signal->count); + current->signal->nr_threads++; atomic_inc(¤t->signal->live); + atomic_inc(¤t->signal->sigcnt); p->group_leader = current->group_leader; list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); }