Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932404AbWBXRew (ORCPT ); Fri, 24 Feb 2006 12:34:52 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932402AbWBXRew (ORCPT ); Fri, 24 Feb 2006 12:34:52 -0500 Received: from e35.co.us.ibm.com ([32.97.110.153]:53146 "EHLO e35.co.us.ibm.com") by vger.kernel.org with ESMTP id S932404AbWBXRev (ORCPT ); Fri, 24 Feb 2006 12:34:51 -0500 Date: Fri, 24 Feb 2006 09:35:19 -0800 From: "Paul E. McKenney" To: Oleg Nesterov Cc: Andrew Morton , linux-kernel@vger.kernel.org, Ingo Molnar , "Eric W. Biederman" , Roland McGrath Subject: Re: [PATCH 1/2] copy_process: cleanup bad_fork_cleanup_sighand Message-ID: <20060224173519.GA1735@us.ibm.com> Reply-To: paulmck@us.ibm.com References: <43F9E841.FD560455@tv-sign.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <43F9E841.FD560455@tv-sign.ru> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2687 Lines: 73 On Mon, Feb 20, 2006 at 07:03:13PM +0300, Oleg Nesterov wrote: > The only caller of exit_sighand(tsk) is copy_process's error path. > We can call __exit_sighand() directly and kill exit_sighand(). > > This 'tsk' was not yet registered in pid_hash[] or init_task.tasks, > it has no external references, nobody can see it, and > > IF (clone_flags & CLONE_SIGHAND) > At least 'current' has a reference to ->sighand, this > means atomic_dec_and_test(sighand->count) can't be true. > > ELSE > Nobody can see this ->sighand, this means we can free it > without any locking. This passes steamroller tests (which now work on ppc64, but that is another story). Looks good to me! Thanx, Paul Acked-by: > Signed-off-by: Oleg Nesterov > > --- 2.6.16-rc3/include/linux/sched.h~1_SIGH 2006-02-18 22:13:44.000000000 +0300 > +++ 2.6.16-rc3/include/linux/sched.h 2006-02-20 00:38:57.000000000 +0300 > @@ -1143,7 +1143,6 @@ extern void exit_thread(void); > extern void exit_files(struct task_struct *); > extern void exit_signal(struct task_struct *); > extern void __exit_signal(struct task_struct *); > -extern void exit_sighand(struct task_struct *); > extern void __exit_sighand(struct task_struct *); > extern void exit_itimers(struct signal_struct *); > > --- 2.6.16-rc3/kernel/signal.c~1_SIGH 2006-02-19 21:08:23.000000000 +0300 > +++ 2.6.16-rc3/kernel/signal.c 2006-02-20 00:37:34.000000000 +0300 > @@ -336,20 +336,6 @@ void __exit_sighand(struct task_struct * > kmem_cache_free(sighand_cachep, sighand); > } > > -void exit_sighand(struct task_struct *tsk) > -{ > - write_lock_irq(&tasklist_lock); > - rcu_read_lock(); > - if (tsk->sighand != NULL) { > - struct sighand_struct *sighand = rcu_dereference(tsk->sighand); > - spin_lock(&sighand->siglock); > - __exit_sighand(tsk); > - spin_unlock(&sighand->siglock); > - } > - rcu_read_unlock(); > - write_unlock_irq(&tasklist_lock); > -} > - > /* > * This function expects the tasklist_lock write-locked. > */ > --- 2.6.16-rc3/kernel/fork.c~1_SIGH 2006-02-18 01:11:59.000000000 +0300 > +++ 2.6.16-rc3/kernel/fork.c 2006-02-20 00:38:39.000000000 +0300 > @@ -1196,7 +1196,8 @@ bad_fork_cleanup_mm: > bad_fork_cleanup_signal: > exit_signal(p); > bad_fork_cleanup_sighand: > - exit_sighand(p); > + if (p->sighand) > + __exit_sighand(p); > bad_fork_cleanup_fs: > exit_fs(p); /* blocking */ > bad_fork_cleanup_files: - 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/