Hi all, Recently, I ran into a problem of running g_serial,that is kernel crashes when running "cat myfile > /dev/ttyGS0" I also found a discussion about the similar problem after some big changes applied to TTY layer. see :http://lkml.org/lkml/2009/6/22/137 It suggests to disable the low_latency mode,but this only solves the problem of "scheduling while atomic", actually, a new problem is introduced after disabling the low_latency mode. see the code snippet in ...gadget/u_serial.c/gs_rx_push() ...... 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; } ...... tty_flip_buffer_push() in tty_buffer.c ...... void tty_flip_buffer_push(struct tty_struct *tty) { unsigned long flags; spin_lock_irqsave(&tty->buf.lock, flags); if (tty->buf.tail != NULL) tty->buf.tail->commit = tty->buf.tail->used; spin_unlock_irqrestore(&tty->buf.lock, flags); if (tty->low_latency) flush_to_ldisc(&tty->buf.work.work); else schedule_delayed_work(&tty->buf.work, 1); } ...... When low_latency is disabled,tty_flip_buffer_push(tty) will hire a work queue to push the buffer,obviously,this is a deferred job. So, it's not proper to wake up the read thread right after calling tty_flip_buffer_push().I have few knowledge about tty stuff. Does anyone here could give some hints on this problem? Thanks a lot! Cliff -- 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
