Bluetooth: Remove useless rx_lock spinlock (7649faff) · Commits · 戴 / test

rx_lock spinlock is only used in hci_uart_tty_receive() which is the receive_buf ldisc callback. hci_uart_tty_receive() is protected from re-entrance by its only caller (flush_to_ldisc() in drivers/tty/tty_buffer.c) which held a mutex (buf->lock) for this section. This lock allows "safe use of the line discipline's receive_buf() method by excluding the buffer work and any pending flush from using the flip buffer." (comments from tty_buffer_lock_exclusive() in drivers/tty/tty_buffer.c) So, no need to double protect this resource with rx_lock. Signed-off-by:

Frederic Danis <frederic.danis@linux.intel.com> Signed-off-by:

Marcel Holtmann <marcel@holtmann.org>

drivers/bluetooth/hci_ldisc.c

+3 −5

Original line number	Diff line number	Diff line
		@@ -470,8 +470,6 @@ static int hci_uart_tty_open(struct tty_struct *tty)
		INIT_WORK(&hu->init_ready, hci_uart_init_work);
		INIT_WORK(&hu->write_work, hci_uart_write_work);

		spin_lock_init(&hu->rx_lock);

		/* Flush any pending characters in the driver and line discipline. */

		/* FIXME: why is this needed. Note don't use ldisc_ref here as the
		@@ -569,14 +567,14 @@ static void hci_uart_tty_receive(struct tty_struct tty, const u8 data,
		if (!test_bit(HCI_UART_PROTO_SET, &hu->flags))
		return;

		spin_lock(&hu->rx_lock);
		/* It does not need a lock here as it is already protected by a mutex in
		* tty caller
		*/
		hu->proto->recv(hu, data, count);

		if (hu->hdev)
		hu->hdev->stat.byte_rx += count;

		spin_unlock(&hu->rx_lock);

		tty_unthrottle(tty);
		}

drivers/bluetooth/hci_uart.h

+0 −1

Original line number	Diff line number	Diff line
		@@ -85,7 +85,6 @@ struct hci_uart {

		struct sk_buff *tx_skb;
		unsigned long tx_state;
		spinlock_t rx_lock;

		unsigned int init_speed;
		unsigned int oper_speed;

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