No longer set low_latency flag as it causes this warning backtrace: WARNING: at kernel/mutex.c:207 __mutex_lock_slowpath+0x6c/0x288() Fix associated locking and wakeups. Signed-off-by: Jon Povey <jon.povey@xxxxxxxxxxxxxxx> --- I just saw another patch has been submitted for this by Maulik Mankad <x0082077@xxxxxx>. This patch goes further with updated comments and wakeup changes. Tested on TI Davinci DM355 (MUSB OTG) Assumptions: 1. Any callbacks are now done from a workqueue, so don't need to drop the lock any more 2. As noted by Cliff Cai http://www.spinics.net/lists/linux-usb/msg26424.html it is not appropriate to wake readers here (tty code will do it if needed?) DB, please review.. Also found a bug in the cleanup routine which I will send another patch for. drivers/usb/gadget/u_serial.c | 15 ++------------- 1 files changed, 2 insertions(+), 13 deletions(-) diff --git a/drivers/usb/gadget/u_serial.c b/drivers/usb/gadget/u_serial.c index ff10d66..3e8dcb5 100644 --- a/drivers/usb/gadget/u_serial.c +++ b/drivers/usb/gadget/u_serial.c @@ -536,17 +536,11 @@ recycle: list_move(&req->list, &port->read_pool); } - /* Push from tty to ldisc; this is immediate with low_latency, and - * may trigger callbacks to this driver ... so drop the spinlock. + /* Push from tty to ldisc; without low_latency set this is handled by + * a workqueue, so we won't get callbacks and can hold port_lock */ if (tty && do_push) { - spin_unlock_irq(&port->port_lock); tty_flip_buffer_push(tty); - wake_up_interruptible(&tty->read_wait); - spin_lock_irq(&port->port_lock); - - /* tty may have been closed */ - tty = port->port_tty; } @@ -784,11 +778,6 @@ static int gs_open(struct tty_struct *tty, struct file *file) port->open_count = 1; port->openclose = false; - /* low_latency means ldiscs work in tasklet context, without - * needing a workqueue schedule ... easier to keep up. - */ - tty->low_latency = 1; - /* if connected, start the I/O stream */ if (port->port_usb) { struct gserial *gser = port->port_usb; -- 1.6.3.3 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
