Re: [PATCH 4/4] Bluetooth: hci_ldisc: make sure we don't loose HCI_UART_TX_WAKEUP events
flat view
From: Marcel Holtmann <marcel@holtmann.org>
Date: 2016-08-30 16:54:02
Also in:
lkml
Hi Boris,
quoted hunk ↗ jump to hunk
The HCI_UART_TX_WAKEUP flag checking is racy and some HCI_UART_TX_WAKEUP events can be lost. Signed-off-by: Boris Brezillon <redacted> --- 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; +
I know this is correct, but I would actually make it visually different.
if (test_bit(UART_TX_WAKEUP, ..) {
/* comment goes here
*/
if (!test_and_set_bit(UART_SENDING, ..)
goto restart;
}
For me with a proper comment that is a lot easier to read and grok that it is correct.
Regards
Marcel