On Thu, Mar 20, 2014 at 01:31:40PM -0400, Peter Hurley wrote:
> [ +cc Huang Shijie ]
>
> On 03/20/2014 01:16 PM, Felipe Balbi wrote:
> >On Thu, Mar 20, 2014 at 04:42:16PM +0000, Alan Cox wrote:
> >>On Thu, 2014-03-20 at 11:34 -0500, Felipe Balbi wrote:
> >>>Hi,
> >>>
> >>>when 8250 driver calls uart_write_wakeup(), the tty port lock is already
> >>>taken. hci_ldisc.c's implementation of ->write_wakeup() calls
> >>>tty->ops->write() to actually send the characters, but that call will
> >>>try to acquire the same port lock again.
> >>>
> >>>Looking at other line disciplines that looks like a bug in hci_ldisc.c.
> >>>Am I correct to assume that ->write_wakeup() is supposed to *just*
> >>>wakeup the bottom half so we handle ->write() in another context ?
> >>>
> >>>Is it legal to call tty->ops->write() from within ->write_wakeup() ?
> >>
> >>It isn't because you might send all the bytes and go
> >>
> >> write
> >> write_wakeup
> >> write
> >> write wakeup
> >> ...
> >>
> >>and recurse
> >
> >cool, so there really is a bug in hci_ldisc. Marcel, any tips on how do
> >you want this to be sorted out ?
>
> hci_uart_tx_wakeup() should perform the I/O as work.
> FWIW, this was reported by Huang Shijie back on Dec 6.
>
> I'd fix it but I have no way to test it.
here's a build-tested only patch which is waiting for testing from other
colleagues who've got a platform to reproduce the problem:
diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index bc68a44..789000d 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -118,10 +118,6 @@ static inline struct sk_buff *hci_uart_dequeue(struct hci_uart *hu)
int hci_uart_tx_wakeup(struct hci_uart *hu)
{
- struct tty_struct *tty = hu->tty;
- struct hci_dev *hdev = hu->hdev;
- struct sk_buff *skb;
-
if (test_and_set_bit(HCI_UART_SENDING, &hu->tx_state)) {
set_bit(HCI_UART_TX_WAKEUP, &hu->tx_state);
return 0;
@@ -129,6 +125,18 @@ int hci_uart_tx_wakeup(struct hci_uart *hu)
BT_DBG("");
+ schedule_work(&hu->write_work);
+
+ return 0;
+}
+
+static void hci_uart_write_work(struct work_struct *work)
+{
+ struct hci_uart *hu = container_of(work, struct hci_uart, init_ready);
+ struct tty_struct *tty = hu->tty;
+ struct hci_dev *hdev = hu->hdev;
+ struct sk_buff *skb;
+
restart:
clear_bit(HCI_UART_TX_WAKEUP, &hu->tx_state);
@@ -153,7 +161,6 @@ restart:
goto restart;
clear_bit(HCI_UART_SENDING, &hu->tx_state);
- return 0;
}
static void hci_uart_init_work(struct work_struct *work)
@@ -289,6 +296,7 @@ static int hci_uart_tty_open(struct tty_struct *tty)
tty->receive_room = 65536;
INIT_WORK(&hu->init_ready, hci_uart_init_work);
+ INIT_WORK(&hu->write_work, hci_uart_write_work);
spin_lock_init(&hu->rx_lock);
diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h
index fffa61f..12df101 100644
--- a/drivers/bluetooth/hci_uart.h
+++ b/drivers/bluetooth/hci_uart.h
@@ -68,6 +68,7 @@ struct hci_uart {
unsigned long hdev_flags;
struct work_struct init_ready;
+ struct work_struct write_work;
struct hci_uart_proto *proto;
void *priv;
--
balbi
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