Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751125AbaKFCdN (ORCPT ); Wed, 5 Nov 2014 21:33:13 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:39032 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750905AbaKFCdL (ORCPT ); Wed, 5 Nov 2014 21:33:11 -0500 Date: Wed, 5 Nov 2014 18:33:10 -0800 From: Greg Kroah-Hartman To: Peter Hurley Cc: Jiri Slaby , One Thousand Gnomes , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org Subject: Re: [PATCH -next v2 10/26] tty: Don't take tty_mutex for tty count changes Message-ID: <20141106023310.GA5035@kroah.com> References: <1413491125-20134-1-git-send-email-peter@hurleysoftware.com> <1415207589-15967-1-git-send-email-peter@hurleysoftware.com> <1415207589-15967-11-git-send-email-peter@hurleysoftware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1415207589-15967-11-git-send-email-peter@hurleysoftware.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 05, 2014 at 12:12:53PM -0500, Peter Hurley wrote: > Holding tty_mutex is no longer required to serialize changes to > the tty_count or to prevent concurrent opens of closing ttys; > tty_lock() is sufficient. > > Reviewed-by: Alan Cox > Signed-off-by: Peter Hurley > --- > drivers/tty/tty_io.c | 6 ------ > 1 file changed, 6 deletions(-) > > diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c > index ea8c6cae8d12..e59de81c39a9 100644 > --- a/drivers/tty/tty_io.c > +++ b/drivers/tty/tty_io.c > @@ -1804,10 +1804,6 @@ int tty_release(struct inode *inode, struct file *filp) > * each iteration we avoid any problems. > */ > while (1) { > - /* Guard against races with tty->count changes elsewhere and > - opens on /dev/tty */ > - > - mutex_lock(&tty_mutex); > tty_lock_pair(tty, o_tty); > tty_closing = tty->count <= 1; > o_tty_closing = o_tty && > @@ -1840,7 +1836,6 @@ int tty_release(struct inode *inode, struct file *filp) > printk(KERN_WARNING "%s: %s: read/write wait queue active!\n", > __func__, tty_name(tty, buf)); > tty_unlock_pair(tty, o_tty); > - mutex_unlock(&tty_mutex); > schedule(); > } > The code in my tree in this section of tty_release() looks a bit different, so I had to hand-apply this patch. I've included the version I used below, please verify I didn't mess it up. thanks, greg k-h diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index ea8c6cae8d12..e59de81c39a9 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1804,10 +1804,6 @@ int tty_release(struct inode *inode, struct file *filp) * each iteration we avoid any problems. */ while (1) { - /* Guard against races with tty->count changes elsewhere and - opens on /dev/tty */ - - mutex_lock(&tty_mutex); tty_lock_pair(tty, o_tty); tty_closing = tty->count <= 1; o_tty_closing = o_tty && @@ -1840,7 +1836,6 @@ int tty_release(struct inode *inode, struct file *filp) printk(KERN_WARNING "%s: %s: read/write wait queue active!\n", __func__, tty_name(tty, buf)); tty_unlock_pair(tty, o_tty); - mutex_unlock(&tty_mutex); schedule(); } @@ -1891,7 +1886,6 @@ int tty_release(struct inode *inode, struct file *filp) read_unlock(&tasklist_lock); } - mutex_unlock(&tty_mutex); tty_unlock_pair(tty, o_tty); /* At this point, the tty->count == 0 should ensure a dead tty cannot be re-opened by a racing opener */ -- 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/