Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755174AbYJCKDR (ORCPT ); Fri, 3 Oct 2008 06:03:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753292AbYJCKDD (ORCPT ); Fri, 3 Oct 2008 06:03:03 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:61870 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753318AbYJCKDA (ORCPT ); Fri, 3 Oct 2008 06:03:00 -0400 Message-ID: <48E5ED4D.4030102@cn.fujitsu.com> Date: Fri, 03 Oct 2008 18:00:45 +0800 From: Lai Jiangshan User-Agent: Thunderbird 2.0.0.17 (Windows/20080914) MIME-Version: 1.0 To: Ingo Molnar , Andrew Morton CC: Linux Kernel Mailing List , "Paul E. McKenney" Subject: [PATCH] signal, procfs: lock_task_sighand() do not need rcu_read_lock() Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3170 Lines: 102 lock_task_sighand() make sure task->sighand is being protected, so we do not need rcu_read_lock(). [ exec() will get task->sighand->siglock before change task->sighand! ] But code using rcu_read_lock() _just_ to protect lock_task_sighand() only appear in procfs. (and some code in procfs use lock_task_sighand() without such redundant protection.) Other subsystem may put lock_task_sighand() into rcu_read_lock() critical region, but these rcu_read_lock() are used for protecting "for_each_process()", "find_task_by_vpid()" etc. , not for protecting lock_task_sighand(). Signed-off-by: Lai Jiangshan --- diff --git a/fs/proc/array.c b/fs/proc/array.c index 71c9be5..1c8d7b5 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -261,7 +261,6 @@ static inline void task_sig(struct seq_file *m, struct task_struct *p) sigemptyset(&ignored); sigemptyset(&caught); - rcu_read_lock(); if (lock_task_sighand(p, &flags)) { pending = p->pending.signal; shpending = p->signal->shared_pending.signal; @@ -272,7 +271,6 @@ static inline void task_sig(struct seq_file *m, struct task_struct *p) qlim = p->signal->rlim[RLIMIT_SIGPENDING].rlim_cur; unlock_task_sighand(p, &flags); } - rcu_read_unlock(); seq_printf(m, "Threads:\t%d\n", num_threads); seq_printf(m, "SigQ:\t%lu/%lu\n", qsize, qlim); diff --git a/fs/proc/base.c b/fs/proc/base.c index a28840b..bb63fa1 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -164,7 +164,6 @@ static struct fs_struct *get_fs_struct(struct task_struct *task) static int get_nr_threads(struct task_struct *tsk) { - /* Must be called with the rcu_read_lock held */ unsigned long flags; int count = 0; @@ -471,14 +470,10 @@ static int proc_pid_limits(struct task_struct *task, char *buffer) struct rlimit rlim[RLIM_NLIMITS]; - rcu_read_lock(); - if (!lock_task_sighand(task,&flags)) { - rcu_read_unlock(); + if (!lock_task_sighand(task, &flags)) return 0; - } memcpy(rlim, task->signal->rlim, sizeof(struct rlimit) * RLIM_NLIMITS); unlock_task_sighand(task, &flags); - rcu_read_unlock(); /* * print the file header @@ -3088,9 +3083,7 @@ static int proc_task_getattr(struct vfsmount *mnt, struct dentry *dentry, struct generic_fillattr(inode, stat); if (p) { - rcu_read_lock(); stat->nlink += get_nr_threads(p); - rcu_read_unlock(); put_task_struct(p); } diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c index bbe6b31..ad958c1 100644 --- a/kernel/sched_debug.c +++ b/kernel/sched_debug.c @@ -333,12 +333,10 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m) unsigned long flags; int num_threads = 1; - rcu_read_lock(); if (lock_task_sighand(p, &flags)) { num_threads = atomic_read(&p->signal->count); unlock_task_sighand(p, &flags); } - rcu_read_unlock(); SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid, num_threads); SEQ_printf(m, -- 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/