Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753591AbZLEUFx (ORCPT ); Sat, 5 Dec 2009 15:05:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752085AbZLEUFs (ORCPT ); Sat, 5 Dec 2009 15:05:48 -0500 Received: from mx1.redhat.com ([209.132.183.28]:59162 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751888AbZLEUFs (ORCPT ); Sat, 5 Dec 2009 15:05:48 -0500 Date: Sat, 5 Dec 2009 15:04:22 -0500 (EST) From: Miloslav Trmac To: Oleg Nesterov Cc: linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Al Viro , James Morris , Alan Cox , Ingo Molnar , Peter Zijlstra , Andrew Morton , Balbir Singh , Alexey Dobriyan , Heiko Carstens , Renaud Lottiaux , Louis Rilling , David Howells , Stanislaw Gruszka , Veaceslav Falico Message-ID: <1166728910.1204311260043462476.JavaMail.root@zmail07.collab.prod.int.phx2.redhat.com> In-Reply-To: <20091205165804.GD23152@redhat.com> Subject: Re: [PATCH v2 4/4] copy_signal cleanup: clean tty_audit_fork() MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.5.5.72] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1403 Lines: 29 ----- "Oleg Nesterov" wrote: > On 12/04, Veaceslav Falico wrote: > > diff --git a/drivers/char/tty_audit.c b/drivers/char/tty_audit.c > > index ac16fbe..283a15b 100644 > > --- a/drivers/char/tty_audit.c > > +++ b/drivers/char/tty_audit.c > > @@ -148,7 +148,6 @@ void tty_audit_fork(struct signal_struct *sig) > > spin_lock_irq(¤t->sighand->siglock); > > sig->audit_tty = current->signal->audit_tty; > > spin_unlock_irq(¤t->sighand->siglock); > > - sig->tty_audit_buf = NULL; > > } > > Off-topic question to this who understands this code. > > But afaics we can also remove ->siglock from this helper and make > it really trivial for being inline. ->siglock buys nothing, we just > read a boolean. In fact, after the quick grep I do not understand > how ->siglock is connected to ->audit_tty. OK, it protects > tty_audit_buf, > but why we always take ->siglock to access ->audit_tty ? AFAIK there is no explicit documentation of the atomicity semantics expected by the Linux kernel (both from the hardware and from the compiler), so every access to the boolean is protected by a lock, to be on the safe side. Mirek -- 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/