Bluetooth: hci_uart: Fix a race for write_work scheduling
In hci_uart_write_work, there is a loop/goto checking the value of
HCI_UART_TX_WAKEUP. If HCI_UART_TX_WAKEUP is set again, it keeps trying
hci_uart_dequeue; otherwise, it clears HCI_UART_SENDING and returns.
In hci_uart_tx_wakeup, if HCI_UART_SENDING is already set, it sets
HCI_UART_TX_WAKEUP, skips schedule_work and assumes the running/pending
hci_uart_write_work worker will do hci_uart_dequeue properly.
However, if the HCI_UART_SENDING check in hci_uart_tx_wakeup is done after
the loop breaks, but before HCI_UART_SENDING is cleared in
hci_uart_write_work, the schedule_work is skipped incorrectly.
Fix this race by changing the order of HCI_UART_SENDING and
HCI_UART_TX_WAKEUP modification.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Fixes: 82f5169bf3d3 ("Bluetooth: hci_uart: add serdev driver support library")
Signed-off-by: Claire Chang <tientzu@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index f83d67e..8be4d807 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -127,10 +127,9 @@ int hci_uart_tx_wakeup(struct hci_uart *hu)
if (!test_bit(HCI_UART_PROTO_READY, &hu->flags))
goto no_schedule;
- if (test_and_set_bit(HCI_UART_SENDING, &hu->tx_state)) {
- set_bit(HCI_UART_TX_WAKEUP, &hu->tx_state);
+ set_bit(HCI_UART_TX_WAKEUP, &hu->tx_state);
+ if (test_and_set_bit(HCI_UART_SENDING, &hu->tx_state))
goto no_schedule;
- }
BT_DBG("");
@@ -174,10 +173,10 @@ static void hci_uart_write_work(struct work_struct *work)
kfree_skb(skb);
}
+ clear_bit(HCI_UART_SENDING, &hu->tx_state);
if (test_bit(HCI_UART_TX_WAKEUP, &hu->tx_state))
goto restart;
- clear_bit(HCI_UART_SENDING, &hu->tx_state);
wake_up_bit(&hu->tx_state, HCI_UART_SENDING);
}