Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751268AbaKFCu2 (ORCPT ); Wed, 5 Nov 2014 21:50:28 -0500 Received: from mailout32.mail01.mtsvc.net ([216.70.64.70]:53839 "EHLO n23.mail01.mtsvc.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751020AbaKFCu0 (ORCPT ); Wed, 5 Nov 2014 21:50:26 -0500 Message-ID: <545AE1EE.30902@hurleysoftware.com> Date: Wed, 05 Nov 2014 21:50:22 -0500 From: Peter Hurley User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Greg Kroah-Hartman 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 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> <20141106023310.GA5035@kroah.com> <545ADF52.9030401@hurleysoftware.com> In-Reply-To: <545ADF52.9030401@hurleysoftware.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Authenticated-User: 990527 peter@hurleysoftware.com X-MT-ID: 8FA290C2A27252AACF65DBC4A42F3CE3735FB2A4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/05/2014 09:39 PM, Peter Hurley wrote: > On 11/05/2014 09:33 PM, Greg Kroah-Hartman wrote: >> 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. > > Although there's nothing wrong with your version, I'm wondering why this > didn't apply cleanly. > > While I go look at your tree, can you check that these patches are > sitting on top of the earlier two patches you applied to your tty-linus > branch; specifically 'tty: Fix high cpu load if tty is unreleasable' and > 'tty: Prevent "read/write wait queue active!" log flooding'? Yep, that's the problem: your 'tty-testing' branch doesn't have the 3 patches from me that you put in your 'tty-linus' branch earlier this evening. Those are: serial: Fix divide-by-zero fault in uart_get_divisor() tty: Fix high cpu load if tty is unreleasable tty: Prevent "read/write wait queue active!" log flooding How can I help fix this? Regards, Peter Hurley >> 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-serial" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- 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/