Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752734Ab3IUSlF (ORCPT ); Sat, 21 Sep 2013 14:41:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60619 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752605Ab3IUSlD (ORCPT ); Sat, 21 Sep 2013 14:41:03 -0400 Date: Sat, 21 Sep 2013 20:34:36 +0200 From: Oleg Nesterov To: Peter Hurley Cc: Andrew Morton , Greg Kroah-Hartman , Jiri Slaby , Linus Torvalds , codonell , Eduard Benes , Karel Srot , Matt Newsome , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] tty: disassociate_ctty() sends the extra SIGCONT Message-ID: <20130921183436.GA13418@redhat.com> References: <20130915155006.GA11913@redhat.com> <20130915155026.GA11917@redhat.com> <5238BDEC.1070400@hurleysoftware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5238BDEC.1070400@hurleysoftware.com> 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 Content-Length: 2876 Lines: 92 Peter, sorry for delay, I was sick. On 09/17, Peter Hurley wrote: > > On 09/15/2013 11:50 AM, Oleg Nesterov wrote: > >> Put the "!on_exit" check back to restore the old behaviour. >> >> Cc: stable@vger.kernel.org # v3.10+ >> Signed-off-by: Oleg Nesterov >> Reported-by: Karel Srot > > Reviewed-by: Peter Hurley Thanks! Can I ask the question? tty_signal_session_leader() is probably fine, but it _looks_ buggy or at least confusing to me. do_each_pid_task(tty->session, PIDTYPE_SID, p) { spin_lock_irq(&p->sighand->siglock); if (p->signal->tty == tty) { p->signal->tty = NULL; /* We defer the dereferences outside fo the tasklist lock */ refs++; } if (!p->signal->leader) { spin_unlock_irq(&p->sighand->siglock); continue; } __group_send_sig_info(SIGHUP, SEND_SIG_PRIV, p); __group_send_sig_info(SIGCONT, SEND_SIG_PRIV, p); put_pid(p->signal->tty_old_pgrp); /* A noop */ spin_lock(&tty->ctrl_lock); tty_pgrp = get_pid(tty->pgrp); I guess this can happen only once, so we could even add WARN_ON(tty_pgrp) before get_pid(). But this look confusing, as if we can do get_pid() multiple times and leak tty->pgrp. if (tty->pgrp) p->signal->tty_old_pgrp = get_pid(tty->pgrp); else? We already did put_pid(tty_old_pgrp), we should clear it. IOW, do you think the patch below makes sense or I missed something? Just curious. Oleg. --- x/drivers/tty/tty_io.c +++ x/drivers/tty/tty_io.c @@ -548,7 +548,7 @@ static int tty_signal_session_leader(str { struct task_struct *p; int refs = 0; - struct pid *tty_pgrp = NULL; + struct pid *tty_pgrp = tty_get_pgrp(tty); read_lock(&tasklist_lock); if (tty->session) { @@ -560,18 +560,12 @@ static int tty_signal_session_leader(str the tasklist lock */ refs++; } - if (!p->signal->leader) { - spin_unlock_irq(&p->sighand->siglock); - continue; + if (p->signal->leader) { + __group_send_sig_info(SIGHUP, SEND_SIG_PRIV, p); + __group_send_sig_info(SIGCONT, SEND_SIG_PRIV, p); + put_pid(p->signal->tty_old_pgrp); /* A noop */ + p->signal->tty_old_pgrp = get_pid(tty_pgrp); } - __group_send_sig_info(SIGHUP, SEND_SIG_PRIV, p); - __group_send_sig_info(SIGCONT, SEND_SIG_PRIV, p); - put_pid(p->signal->tty_old_pgrp); /* A noop */ - spin_lock(&tty->ctrl_lock); - tty_pgrp = get_pid(tty->pgrp); - if (tty->pgrp) - p->signal->tty_old_pgrp = get_pid(tty->pgrp); - spin_unlock(&tty->ctrl_lock); spin_unlock_irq(&p->sighand->siglock); } while_each_pid_task(tty->session, PIDTYPE_SID, p); } -- 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/