Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753040AbaGNF4D (ORCPT ); Mon, 14 Jul 2014 01:56:03 -0400 Received: from g2t1383g.austin.hp.com ([15.217.136.92]:7427 "EHLO g2t1383g.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752573AbaGNFz4 (ORCPT ); Mon, 14 Jul 2014 01:55:56 -0400 From: "Li, Zhen-Hua" To: , , Cc: "Li, Zhen-Hua" Subject: [PATCH 1/1] driver/tty: Fix a warning in check_tty_count Date: Mon, 14 Jul 2014 13:54:17 +0800 Message-Id: <1405317257-5491-1-git-send-email-zhen-hual@hp.com> X-Mailer: git-send-email 2.0.0-rc0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When there are to many open/close on a tty device in the same time, there may be a warning like: Warning: dev (ttyS0) tty->count(4) != #fd's(3) in tty_release_dev That's because tty->count and files in tty->tty_files are not synchronized in time. So I add a lock to avoid this. Signed-off-by: Li, Zhen-Hua --- drivers/tty/tty_io.c | 13 +++++++++---- include/linux/tty.h | 1 + 2 files changed, 10 insertions(+), 4 deletions(-) diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 3411071..9283fc2 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -297,6 +297,7 @@ static int check_tty_count(struct tty_struct *tty, const char *routine) struct list_head *p; int count = 0; + spin_lock(&tty->count_lock); spin_lock(&tty_files_lock); list_for_each(p, &tty->tty_files) { count++; @@ -310,8 +311,10 @@ static int check_tty_count(struct tty_struct *tty, const char *routine) printk(KERN_WARNING "Warning: dev (%s) tty->count(%d) " "!= #fd's(%d) in %s\n", tty->name, tty->count, count, routine); + spin_unlock(&tty->count_lock); return count; } + spin_unlock(&tty->count_lock); #endif return 0; } @@ -1337,7 +1340,6 @@ int tty_standard_install(struct tty_driver *driver, struct tty_struct *tty) return ret; tty_driver_kref_get(driver); - tty->count++; driver->ttys[tty->index] = tty; return 0; } @@ -1408,7 +1410,6 @@ static int tty_reopen(struct tty_struct *tty) tty->link->count++; } - tty->count++; WARN_ON(!tty->ldisc); @@ -1796,6 +1797,7 @@ int tty_release(struct inode *inode, struct file *filp) * We must *not* drop the tty_mutex until we ensure that a further * entry into tty_open can not pick up this tty. */ + spin_lock(&tty->count_lock); if (pty_master) { if (--o_tty->count < 0) { printk(KERN_WARNING "%s: bad pty slave count (%d) for %s\n", @@ -1819,7 +1821,7 @@ int tty_release(struct inode *inode, struct file *filp) * something that needs to be handled for hangups. */ tty_del_file(filp); - + spin_unlock(&tty->count_lock); /* * Perform some housekeeping before deciding whether to return. * @@ -2046,8 +2048,10 @@ retry_open: retval = PTR_ERR(tty); goto err_file; } - + spin_lock(&tty->count_lock); + tty->count++; tty_add_file(tty, filp); + spin_unlock(&tty->count_lock); check_tty_count(tty, __func__); if (tty->driver->type == TTY_DRIVER_TYPE_PTY && @@ -3031,6 +3035,7 @@ void initialize_tty_struct(struct tty_struct *tty, INIT_WORK(&tty->hangup_work, do_tty_hangup); mutex_init(&tty->atomic_write_lock); spin_lock_init(&tty->ctrl_lock); + spin_lock_init(&tty->count_lock); INIT_LIST_HEAD(&tty->tty_files); INIT_WORK(&tty->SAK_work, do_SAK_work); diff --git a/include/linux/tty.h b/include/linux/tty.h index 1c3316a..2959300 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -284,6 +284,7 @@ struct tty_struct { /* If the tty has a pending do_SAK, queue it here - akpm */ struct work_struct SAK_work; struct tty_port *port; + spinlock_t count_lock; }; /* Each of a tty's open files has private_data pointing to tty_file_private */ -- 2.0.0-rc0 -- 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/