Hi, after upgrading from Kernel 3.5 to Kernel 3.8 (actually updating kubuntu 12.10 to 13.04) I am having the problem, that some times tcdrain does not return. To be more precise: I am having an application which polls some devices on a RS485-bus. It does this by sending 3 Bytes, calling tcdrain and then waiting for the answer / timeout. This worked flawlessly on kernels up to 3.5. With kernel 3.8 regularly the application hangs because tcdrain does not return. dmesg-log with usbserial and ftdi_sio with debug on: Jun 26 17:28:03 tupai kernel: [25094.164268] ftdi_sio ttyUSB0: ftdi_get_modem_status - 0x0260 Jun 26 17:28:03 tupai kernel: [25094.164274] ftdi_sio ttyUSB0: ftdi_chars_in_buffer - 0 Jun 26 17:28:03 tupai kernel: [25094.164280] tty ttyUSB0: serial_write_room - port 0 Jun 26 17:28:03 tupai kernel: [25094.164300] tty ttyUSB0: serial_write - port 0, 3 byte(s) Jun 26 17:28:03 tupai kernel: [25094.164314] tty ttyUSB0: serial_chars_in_buffer - port 0 Jun 26 17:28:03 tupai kernel: [25094.164318] ftdi_sio ttyUSB0: ftdi_chars_in_buffer - 3 Jun 26 17:28:03 tupai kernel: [25094.164322] tty ttyUSB0: serial_chars_in_buffer - port 0 Jun 26 17:28:03 tupai kernel: [25094.164326] ftdi_sio ttyUSB0: ftdi_chars_in_buffer - 3 Jun 26 17:28:03 tupai kernel: [25094.164363] tty ttyUSB0: usb_serial_port_work - port 0 Jun 26 17:28:03 tupai kernel: [25094.164384] tty ttyUSB0: serial_chars_in_buffer - port 0 Jun 26 17:28:03 tupai kernel: [25094.164535] ftdi_sio ttyUSB0: ftdi_get_modem_status - 0x0200 Jun 26 17:28:03 tupai kernel: [25094.164541] ftdi_sio ttyUSB0: ftdi_chars_in_buffer - 1 --> Application blocks (tcdrain does not return). My guess is, that the waitqueue which is used in the call to wait_event_interruptible_timeout in the function tty_wait_until_sent does not reliably get triggered, when the modem status changes the FTDI_RS_TEMT flag. Is this a know bug? Is this already addressed by the changes which are discussed in the thread "Re: Regression: ftdi_sio is slow (since Wed Oct 10 15:05:06 2012)" ? Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
