Return-Path: From: Dean Jenkins To: Marcel Holtmann CC: Dean Jenkins , "Gustavo F . Padovan" , Johan Hedberg , Subject: [PATCH V1 3/3] Bluetooth: hci_ldisc: Add protocol check to hci_uart_tx_wakeup() Date: Fri, 28 Apr 2017 13:57:26 +0100 Message-ID: <1493384246-15381-4-git-send-email-Dean_Jenkins@mentor.com> In-Reply-To: <1493384246-15381-1-git-send-email-Dean_Jenkins@mentor.com> References: <1493384246-15381-1-git-send-email-Dean_Jenkins@mentor.com> MIME-Version: 1.0 Content-Type: text/plain List-ID: Before attempting to schedule a work-item onto hu->write_work in hci_uart_tx_wakeup(), check that the Data Link protocol layer is still bound to the HCI UART driver. Failure to perform this protocol check causes a race condition between the work queue hu->write_work running hci_uart_write_work() and the Data Link protocol layer being unbound (closed) in hci_uart_tty_close(). Note hci_uart_tty_close() does have a "cancel_work_sync(&hu->write_work)" but it is ineffective because it cannot prevent work-items being added to hu->write_work after cancel_work_sync() has run. Therefore, add a check for HCI_UART_PROTO_READY into hci_uart_tx_wakeup() which prevents scheduling of the work queue when HCI_UART_PROTO_READY is in the clear state. However, note a small race condition remains because the hci_uart_tx_wakeup() thread can run in parallel with the hci_uart_tty_close() thread so it is possible that a schedule of hu->write_work can occur when HCI_UART_PROTO_READY is cleared. A complete solution needs locking of the threads which is implemented in a future commit. Signed-off-by: Dean Jenkins --- drivers/bluetooth/hci_ldisc.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c index 6f9e406..2edd305 100644 --- a/drivers/bluetooth/hci_ldisc.c +++ b/drivers/bluetooth/hci_ldisc.c @@ -125,6 +125,9 @@ static inline struct sk_buff *hci_uart_dequeue(struct hci_uart *hu) int hci_uart_tx_wakeup(struct hci_uart *hu) { + if (!test_bit(HCI_UART_PROTO_READY, &hu->flags)) + return 0; + if (test_and_set_bit(HCI_UART_SENDING, &hu->tx_state)) { set_bit(HCI_UART_TX_WAKEUP, &hu->tx_state); return 0; -- 2.7.4