From c65c9bc3efa5589f691276bb9db689119a711222 Mon Sep 17 00:00:00 2001 From: Alan Cox Date: Thu, 11 Jun 2009 12:50:12 +0100 Subject: tty: rewrite the ldisc locking There are several pretty much unfixable races in the old ldisc code, especially with respect to pty behaviour and also to hangup. It's easier to rewrite the code than simply try and patch it up. This patch - splits the ldisc from the tty (so we will be able to refcount it more cleanly later) - introduces a mutex lock for ldisc changing on an active device - fixes the complete mess that hangup caused - implements hopefully correct setldisc/close/hangup locking There are still some problems around pty pairs that have always been there but at least it is now possible to understand the code and fix further problems. This fixes the following known bugs - hang up can leak ldisc references - hang up may not call open/close on ldisc in a matched way - pty/tty pairs can deadlock during an ldisc change - reading the ldisc proc files can cause every ldisc to be loaded and probably a few other of the mysterious ldisc race reports. I'm sure it also adds the odd new one. Signed-off-by: Alan Cox Signed-off-by: Linus Torvalds --- drivers/char/n_hdlc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'drivers/char/n_hdlc.c') diff --git a/drivers/char/n_hdlc.c b/drivers/char/n_hdlc.c index bacb3e2872a..461ece591a5 100644 --- a/drivers/char/n_hdlc.c +++ b/drivers/char/n_hdlc.c @@ -342,8 +342,8 @@ static int n_hdlc_tty_open (struct tty_struct *tty) #endif /* Flush any pending characters in the driver and discipline. */ - if (tty->ldisc.ops->flush_buffer) - tty->ldisc.ops->flush_buffer(tty); + if (tty->ldisc->ops->flush_buffer) + tty->ldisc->ops->flush_buffer(tty); tty_driver_flush_buffer(tty); -- cgit v1.2.3-70-g09d2 From be10eb7589337e5defbe214dae038a53dd21add8 Mon Sep 17 00:00:00 2001 From: Paul Fulghum Date: Mon, 22 Jun 2009 18:42:56 +0100 Subject: tty: n_hdlc add buffer flushing Add flush_buffer tty callback to flush rx buffers. Add TCFLSH ioctl processing to flush tx buffers. Increase default tx buffers from 1 to 3. Remove unneeded flush_buffer call in open callback. Remove vendor specific CVS version string. Signed-off-by: Paul Fulghum Signed-off-by: Alan Cox Signed-off-by: Linus Torvalds --- drivers/char/n_hdlc.c | 46 +++++++++++++++++++++++++++++++++++++--------- 1 file changed, 37 insertions(+), 9 deletions(-) (limited to 'drivers/char/n_hdlc.c') diff --git a/drivers/char/n_hdlc.c b/drivers/char/n_hdlc.c index 461ece591a5..1c43c8cdee2 100644 --- a/drivers/char/n_hdlc.c +++ b/drivers/char/n_hdlc.c @@ -10,7 +10,6 @@ * Paul Mackerras * * Original release 01/11/99 - * $Id: n_hdlc.c,v 4.8 2003/05/06 21:18:51 paulkf Exp $ * * This code is released under the GNU General Public License (GPL) * @@ -79,7 +78,6 @@ */ #define HDLC_MAGIC 0x239e -#define HDLC_VERSION "$Revision: 4.8 $" #include #include @@ -114,7 +112,7 @@ #define MAX_HDLC_FRAME_SIZE 65535 #define DEFAULT_RX_BUF_COUNT 10 #define MAX_RX_BUF_COUNT 60 -#define DEFAULT_TX_BUF_COUNT 1 +#define DEFAULT_TX_BUF_COUNT 3 struct n_hdlc_buf { struct n_hdlc_buf *link; @@ -199,6 +197,31 @@ static void n_hdlc_tty_wakeup(struct tty_struct *tty); #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data)) #define n_hdlc2tty(n_hdlc) ((n_hdlc)->tty) +static void flush_rx_queue(struct tty_struct *tty) +{ + struct n_hdlc *n_hdlc = tty2n_hdlc(tty); + struct n_hdlc_buf *buf; + + while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list))) + n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf); +} + +static void flush_tx_queue(struct tty_struct *tty) +{ + struct n_hdlc *n_hdlc = tty2n_hdlc(tty); + struct n_hdlc_buf *buf; + unsigned long flags; + + while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list))) + n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf); + spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); + if (n_hdlc->tbuf) { + n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, n_hdlc->tbuf); + n_hdlc->tbuf = NULL; + } + spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); +} + static struct tty_ldisc_ops n_hdlc_ldisc = { .owner = THIS_MODULE, .magic = TTY_LDISC_MAGIC, @@ -211,6 +234,7 @@ static struct tty_ldisc_ops n_hdlc_ldisc = { .poll = n_hdlc_tty_poll, .receive_buf = n_hdlc_tty_receive, .write_wakeup = n_hdlc_tty_wakeup, + .flush_buffer = flush_rx_queue, }; /** @@ -341,10 +365,7 @@ static int n_hdlc_tty_open (struct tty_struct *tty) set_bit(TTY_NO_WRITE_SPLIT,&tty->flags); #endif - /* Flush any pending characters in the driver and discipline. */ - if (tty->ldisc->ops->flush_buffer) - tty->ldisc->ops->flush_buffer(tty); - + /* flush receive data from driver */ tty_driver_flush_buffer(tty); if (debuglevel >= DEBUG_LEVEL_INFO) @@ -763,6 +784,14 @@ static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file, error = put_user(count, (int __user *)arg); break; + case TCFLSH: + switch (arg) { + case TCIOFLUSH: + case TCOFLUSH: + flush_tx_queue(tty); + } + /* fall through to default */ + default: error = n_tty_ioctl_helper(tty, file, cmd, arg); break; @@ -919,8 +948,7 @@ static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list) } /* end of n_hdlc_buf_get() */ static char hdlc_banner[] __initdata = - KERN_INFO "HDLC line discipline: version " HDLC_VERSION - ", maxframe=%u\n"; + KERN_INFO "HDLC line discipline maxframe=%u\n"; static char hdlc_register_ok[] __initdata = KERN_INFO "N_HDLC line discipline registered.\n"; static char hdlc_register_fail[] __initdata = -- cgit v1.2.3-70-g09d2