usb: gadget: u_serial: use mutex for serialising open()s (c6561082) · Commits · 戴 / test

drivers/usb/gadget/function/u_serial.c

+37 −75

Original line number	Diff line number	Diff line
		@@ -104,7 +104,6 @@ struct gs_port {
		struct gs_console *console;
		#endif

		bool openclose; /* open/close in progress */
		u8 port_num;

		struct list_head read_pool;
		@@ -588,82 +587,45 @@ static int gs_open(struct tty_struct tty, struct file file)
		{
		int port_num = tty->index;
		struct gs_port *port;
		int status;
		int status = 0;

		do {
		mutex_lock(&ports[port_num].lock);
		port = ports[port_num].port;
		if (!port)
		if (!port) {
		status = -ENODEV;
		else {
		spin_lock_irq(&port->port_lock);

		/* already open? Great. */
		if (port->port.count) {
		status = 0;
		port->port.count++;

		/* currently opening/closing? wait ... */
		} else if (port->openclose) {
		status = -EBUSY;

		/* ... else we do the work */
		} else {
		status = -EAGAIN;
		port->openclose = true;
		}
		spin_unlock_irq(&port->port_lock);
		}
		mutex_unlock(&ports[port_num].lock);

		switch (status) {
		default:
		/* fully handled */
		return status;
		case -EAGAIN:
		/* must do the work */
		break;
		case -EBUSY:
		/* wait for EAGAIN task to finish */
		msleep(1);
		/* REVISIT could have a waitchannel here, if
		* concurrent open performance is important
		*/
		break;
		goto out;
		}
		} while (status != -EAGAIN);

		/* Do the "real open" */
		spin_lock_irq(&port->port_lock);

		/* allocate circular buffer on first open */
		if (!kfifo_initialized(&port->port_write_buf)) {

		spin_unlock_irq(&port->port_lock);

		/*
		* portmaster's mutex still protects from simultaneous open(),
		* and close() can't happen, yet.
		*/

		status = kfifo_alloc(&port->port_write_buf,
		WRITE_BUF_SIZE, GFP_KERNEL);
		spin_lock_irq(&port->port_lock);

		if (status) {
		pr_debug("gs_open: ttyGS%d (%p,%p) no buffer\n",
		port->port_num, tty, file);
		port->openclose = false;
		goto exit_unlock_port;
		}
		port_num, tty, file);
		goto out;
		}

		/* REVISIT if REMOVED (ports[].port NULL), abort the open
		* to let rmmod work faster (but this way isn't wrong).
		*/
		spin_lock_irq(&port->port_lock);
		}

		/* REVISIT maybe wait for "carrier detect" */
		/* already open? Great. */
		if (port->port.count++)
		goto exit_unlock_port;

		tty->driver_data = port;
		port->port.tty = tty;

		port->port.count = 1;
		port->openclose = false;

		/* if connected, start the I/O stream */
		if (port->port_usb) {
		struct gserial *gser = port->port_usb;
		@@ -677,20 +639,21 @@ static int gs_open(struct tty_struct tty, struct file file)

		pr_debug("gs_open: ttyGS%d (%p,%p)\n", port->port_num, tty, file);

		status = 0;

		exit_unlock_port:
		spin_unlock_irq(&port->port_lock);
		out:
		mutex_unlock(&ports[port_num].lock);
		return status;
		}

		static int gs_writes_finished(struct gs_port *p)
		static int gs_close_flush_done(struct gs_port *p)
		{
		int cond;

		/* return true on disconnect or empty buffer */
		/* return true on disconnect or empty buffer or if raced with open() */
		spin_lock_irq(&p->port_lock);
		cond = (p->port_usb == NULL) \|\| !kfifo_len(&p->port_write_buf);
		cond = p->port_usb == NULL \|\| !kfifo_len(&p->port_write_buf) \|\|
		p->port.count > 1;
		spin_unlock_irq(&p->port_lock);

		return cond;
		@@ -704,6 +667,7 @@ static void gs_close(struct tty_struct tty, struct file file)
		spin_lock_irq(&port->port_lock);

		if (port->port.count != 1) {
		raced_with_open:
		if (port->port.count == 0)
		WARN_ON(1);
		else
		@@ -713,12 +677,6 @@ static void gs_close(struct tty_struct tty, struct file file)

		pr_debug("gs_close: ttyGS%d (%p,%p) ...\n", port->port_num, tty, file);

		/* mark port as closing but in use; we can drop port lock
		* and sleep if necessary
		*/
		port->openclose = true;
		port->port.count = 0;

		gser = port->port_usb;
		if (gser && gser->disconnect)
		gser->disconnect(gser);
		@@ -729,9 +687,13 @@ static void gs_close(struct tty_struct tty, struct file file)
		if (kfifo_len(&port->port_write_buf) > 0 && gser) {
		spin_unlock_irq(&port->port_lock);
		wait_event_interruptible_timeout(port->drain_wait,
		gs_writes_finished(port),
		gs_close_flush_done(port),
		GS_CLOSE_TIMEOUT * HZ);
		spin_lock_irq(&port->port_lock);

		if (port->port.count != 1)
		goto raced_with_open;

		gser = port->port_usb;
		}

		@@ -744,10 +706,9 @@ static void gs_close(struct tty_struct tty, struct file file)
		else
		kfifo_reset(&port->port_write_buf);

		port->port.count = 0;
		port->port.tty = NULL;

		port->openclose = false;

		pr_debug("gs_close: ttyGS%d (%p,%p) done!\n",
		port->port_num, tty, file);

		@@ -1207,8 +1168,9 @@ static int gs_closed(struct gs_port *port)
		int cond;

		spin_lock_irq(&port->port_lock);
		cond = (port->port.count == 0) && !port->openclose;
		cond = port->port.count == 0;
		spin_unlock_irq(&port->port_lock);

		return cond;
		}

		@@ -1413,7 +1375,7 @@ void gserial_disconnect(struct gserial *gser)

		port->port_usb = NULL;
		gser->ioport = NULL;
		if (port->port.count > 0 \|\| port->openclose) {
		if (port->port.count > 0) {
		wake_up_interruptible(&port->drain_wait);
		if (port->port.tty)
		tty_hangup(port->port.tty);
		@@ -1426,7 +1388,7 @@ void gserial_disconnect(struct gserial *gser)

		/* finally, free any unused/unusable I/O buffers */
		spin_lock_irqsave(&port->port_lock, flags);
		if (port->port.count == 0 && !port->openclose)
		if (port->port.count == 0)
		kfifo_free(&port->port_write_buf);
		gs_free_requests(gser->out, &port->read_pool, NULL);
		gs_free_requests(gser->out, &port->read_queue, NULL);

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