From c6561082b833afde1469346c7e65e0e6b04fc322 Mon Sep 17 00:00:00 2001 From: Michał Mirosław Date: Sat, 10 Aug 2019 10:42:53 +0200 Subject: usb: gadget: u_serial: use mutex for serialising open()s MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Remove home-made waiting mechanism from gs_open() and rely on portmaster's mutex to do the job. Note: This releases thread waiting on close() when another thread open()s simultaneously. Signed-off-by: Michał Mirosław Signed-off-by: Felipe Balbi --- drivers/usb/gadget/function/u_serial.c | 112 +++++++++++---------------------- 1 file changed, 37 insertions(+), 75 deletions(-) (limited to 'drivers/usb/gadget') diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c index a248ed0fd5d2..f986e5c55974 100644 --- a/drivers/usb/gadget/function/u_serial.c +++ b/drivers/usb/gadget/function/u_serial.c @@ -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; - - do { - mutex_lock(&ports[port_num].lock); - port = ports[port_num].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); + int status = 0; - 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; - } - } while (status != -EAGAIN); + mutex_lock(&ports[port_num].lock); + port = ports[port_num].port; + if (!port) { + status = -ENODEV; + goto out; + } - /* 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); -- cgit v1.2.3