linux-kernel - [PATCH 4/4] Bluetooth: hci_ldisc: make sure we don't loose HCI_UART_TX

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Date:   Fri, 19 Aug 2016 09:38:47 +0200
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Marcel Holtmann <marcel@...tmann.org>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        linux-bluetooth@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, jason.abele@...il.com,
        Boris Brezillon <boris.brezillon@...e-electrons.com>
Subject: [PATCH 4/4] Bluetooth: hci_ldisc: make sure we don't loose HCI_UART_TX_WAKEUP events

The HCI_UART_TX_WAKEUP flag checking is racy and some HCI_UART_TX_WAKEUP
events can be lost.

Signed-off-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
---
 drivers/bluetooth/hci_ldisc.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index 27f73294edcb..ee7b25f1c6ce 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -172,6 +172,17 @@ restart:
 		goto restart;
 
 	clear_bit(HCI_UART_SENDING, &hu->tx_state);
+
+	/*
+	 * One last check to make sure hci_uart_tx_wakeup() did not set
+	 * HCI_UART_TX_WAKEUP while we where clearing HCI_UART_SENDING.
+	 * The work might have been scheduled by someone else in the
+	 * meantime, in this case we return directly.
+	 */
+	if (test_bit(HCI_UART_TX_WAKEUP, &hu->tx_state) &&
+	    !test_and_set_bit(HCI_UART_SENDING, &hu->tx_state))
+		goto restart;
+
 }
 
 static void hci_uart_init_work(struct work_struct *work)
-- 
2.7.4