Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752308AbaGGJHk (ORCPT ); Mon, 7 Jul 2014 05:07:40 -0400 Received: from mail-wg0-f47.google.com ([74.125.82.47]:33528 "EHLO mail-wg0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752176AbaGGJHe (ORCPT ); Mon, 7 Jul 2014 05:07:34 -0400 From: Olivier Sobrie To: Jan Dumon , linux-usb@vger.kernel.org, netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Olivier Sobrie Subject: [PATCH 2/2] hso: fix deadlock when receiving bursts of data Date: Mon, 7 Jul 2014 11:06:07 +0200 Message-Id: <1404723967-24245-2-git-send-email-olivier@sobrie.be> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1404723967-24245-1-git-send-email-olivier@sobrie.be> References: <1404723967-24245-1-git-send-email-olivier@sobrie.be> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When the module sends bursts of data, sometimes a deadlock happens in the hso driver when the tty buffer doesn't get the chance to be flushed quickly enough. To avoid this, first, we remove the endless while loop in put_rx_bufdata() which is the root cause of the deadlock. Secondly, when there is no room anymore in the tty buffer, we set up a timer of 100 msecs to give a chance to the upper layer to flush the tty buffer and make room for new data. Signed-off-by: Olivier Sobrie --- drivers/net/usb/hso.c | 51 +++++++++++++++++++++++++++++++++---------------- 1 file changed, 35 insertions(+), 16 deletions(-) diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c index 9ca2b41..1dff74f 100644 --- a/drivers/net/usb/hso.c +++ b/drivers/net/usb/hso.c @@ -106,6 +106,8 @@ #define MAX_RX_URBS 2 +#define UNTHROTTLE_TIMEOUT 100 /* msecs */ + /*****************************************************************************/ /* Debugging functions */ /*****************************************************************************/ @@ -261,6 +263,7 @@ struct hso_serial { u16 curr_rx_urb_offset; u8 rx_urb_filled[MAX_RX_URBS]; struct tasklet_struct unthrottle_tasklet; + struct timer_list unthrottle_timer; }; struct hso_device { @@ -1161,13 +1164,18 @@ static void put_rxbuf_data_and_resubmit_bulk_urb(struct hso_serial *serial) while (serial->rx_urb_filled[serial->curr_rx_urb_idx]) { curr_urb = serial->rx_urb[serial->curr_rx_urb_idx]; count = put_rxbuf_data(curr_urb, serial); - if (count == -1) - return; if (count == 0) { serial->curr_rx_urb_idx++; if (serial->curr_rx_urb_idx >= serial->num_rx_urbs) serial->curr_rx_urb_idx = 0; hso_resubmit_rx_bulk_urb(serial, curr_urb); + } else if (count > 0) { + mod_timer(&serial->unthrottle_timer, + jiffies + + msecs_to_jiffies(UNTHROTTLE_TIMEOUT)); + break; + } else { + break; } } } @@ -1251,6 +1259,11 @@ static void hso_unthrottle(struct tty_struct *tty) tasklet_hi_schedule(&serial->unthrottle_tasklet); } +static void hso_unthrottle_schedule(unsigned long data) +{ + tasklet_schedule((struct tasklet_struct *)data); +} + /* open the requested serial port */ static int hso_serial_open(struct tty_struct *tty, struct file *filp) { @@ -1286,6 +1299,10 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp) tasklet_init(&serial->unthrottle_tasklet, (void (*)(unsigned long))hso_unthrottle_tasklet, (unsigned long)serial); + serial->unthrottle_timer.function = hso_unthrottle_schedule; + serial->unthrottle_timer.data = + (unsigned long)&serial->unthrottle_tasklet; + init_timer(&serial->unthrottle_timer); result = hso_start_serial_device(serial->parent, GFP_KERNEL); if (result) { hso_stop_serial_device(serial->parent); @@ -1333,6 +1350,7 @@ static void hso_serial_close(struct tty_struct *tty, struct file *filp) tty_port_tty_set(&serial->port, NULL); if (!usb_gone) hso_stop_serial_device(serial->parent); + del_timer_sync(&serial->unthrottle_timer); tasklet_kill(&serial->unthrottle_tasklet); } @@ -2012,22 +2030,23 @@ static int put_rxbuf_data(struct urb *urb, struct hso_serial *serial) tty = tty_port_tty_get(&serial->port); + if (tty && test_bit(TTY_THROTTLED, &tty->flags)) { + tty_kref_put(tty); + return -1; + } + /* Push data to tty */ - write_length_remaining = urb->actual_length - - serial->curr_rx_urb_offset; D1("data to push to tty"); - while (write_length_remaining) { - if (tty && test_bit(TTY_THROTTLED, &tty->flags)) { - tty_kref_put(tty); - return -1; - } - curr_write_len = tty_insert_flip_string(&serial->port, - urb->transfer_buffer + serial->curr_rx_urb_offset, - write_length_remaining); - serial->curr_rx_urb_offset += curr_write_len; - write_length_remaining -= curr_write_len; - tty_flip_buffer_push(&serial->port); - } + write_length_remaining = urb->actual_length - + serial->curr_rx_urb_offset; + curr_write_len = + tty_insert_flip_string(&serial->port, + urb->transfer_buffer + + serial->curr_rx_urb_offset, + write_length_remaining); + serial->curr_rx_urb_offset += curr_write_len; + write_length_remaining -= curr_write_len; + tty_flip_buffer_push(&serial->port); tty_kref_put(tty); if (write_length_remaining == 0) { -- 1.7.9.5 -- 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/