From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754985Ab1LJAwN (ORCPT ); Fri, 9 Dec 2011 19:52:13 -0500 Received: from mail-ey0-f202.google.com ([209.85.215.202]:38950 "EHLO mail-ey0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752673Ab1LJAwM (ORCPT ); Fri, 9 Dec 2011 19:52:12 -0500 From: Havard Skinnemoen To: gregkh@suse.de Cc: alan@linux.intel.com, davej@redhat.com, jslaby@suse.cz, linux-kernel@vger.kernel.org, Havard Skinnemoen Subject: [PATCH] cdc-acm: Kill ACM_READY() macro completely Date: Fri, 9 Dec 2011 16:51:54 -0800 Message-Id: <1323478314-29443-1-git-send-email-hskinnemoen@google.com> X-Mailer: git-send-email 1.7.3.1 In-Reply-To: <13234763473078@kroah.org> References: <13234763473078@kroah.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The ACM_READY() macro doesn't seem to do anything useful, and it may prevent tty_wait_until_sent() from working properly when called from close. Previously, acm_tty_chars_in_buffer() returned 0 whenever acm->port.count was 0. This means close() could return before all the data has actually been written. Signed-off-by: Havard Skinnemoen --- Hi Greg, Thanks for picking up my patch. Unfortunately, it's not completely bug-free. This fixes an issue I found while testing the patch: After writing something to /dev/ttyACM0, the process would hang for a fairly long time (10-15 seconds) when closing the device. This is because port.count drops to 0 before tty_wait_until_sent_from_close() is called, which causes ACM_READY() to return false, any outstanding writes never get reaped because the workqueue doesn't get scheduled, tty_wait_until_sent never sees any progress and eventually times out. Please feel free to fold this into "cdc-acm: Fix potential deadlock (lockdep warning)", or let me know if you want me to send you a v2 of that patch instead. drivers/usb/class/cdc-acm.c | 10 +--------- 1 files changed, 1 insertions(+), 9 deletions(-) diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 3027ada..d9d9340 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -60,8 +60,6 @@ static struct acm *acm_table[ACM_TTY_MINORS]; static DEFINE_MUTEX(acm_table_lock); -#define ACM_READY(acm) (acm && acm->dev && acm->port.count) - /* * acm_table accessors */ @@ -319,9 +317,6 @@ static void acm_ctrl_irq(struct urb *urb) goto exit; } - if (!ACM_READY(acm)) - goto exit; - usb_mark_last_busy(acm->dev); data = (unsigned char *)(dr + 1); @@ -481,8 +476,7 @@ static void acm_write_bulk(struct urb *urb) spin_lock_irqsave(&acm->write_lock, flags); acm_write_done(acm, wb); spin_unlock_irqrestore(&acm->write_lock, flags); - if (ACM_READY(acm)) - schedule_work(&acm->work); + schedule_work(&acm->work); } static void acm_softint(struct work_struct *work) @@ -492,8 +486,6 @@ static void acm_softint(struct work_struct *work) dev_vdbg(&acm->data->dev, "%s\n", __func__); - if (!ACM_READY(acm)) - return; tty = tty_port_tty_get(&acm->port); if (!tty) return; -- 1.7.3.1