Re: open() on /dev/tty takes 30 seconds on 2.6.36

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From: Eli Billauer
Date: Tuesday, November 2, 2010 - 5:15 pm

Arnd Bergmann wrote:

I lost you here. Maybe my version is outdated? The most similar thing I 
have is this in tty_port.c, in tty_port_close_start():

    if (test_bit(ASYNCB_INITIALIZED, &port->flags) &&
            port->closing_wait != ASYNC_CLOSING_WAIT_NONE)
        tty_wait_until_sent(tty, port->closing_wait);

I put a printk on invocations of tty_wait_until_sent(), which was called 
like crazy during bootup on behalf of tty1, and then never again after 
boot was completed. I should point out, that during this session, all I 
did was to wait a few minutes and then reboot the computer from the GUI 
login console. So I never logged in. Anyhow, the ttySx ports were opened 
and closed, the same 30 seconds delays, but no call to 
tty_wait_until_sent() until kernel logging was stopped.

It turns out, that the device, to which ttyS1-ttyS3 are attached is a 
soft modem, which doesn't even have drivers for a 64 bits system. There 
is no /dev/ttyS4, which is consistent with the "Couldn't register serial 
port 0000:05:04.0: -28" message. Anyhow, I can't say I understand why 
any serial port was allocated to this modem. But it's not like I 
understand how it should work.

05:04.0 Modem: ALi Corporation SmartLink SmartPCI563 56K Modem (prog-if 
00 [Generic])
    Subsystem: Device 2020:545a
    Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- 
Stepping- SERR- FastB2B- DisINTx-
    Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- 
<TAbort- <MAbort- >SERR- <PERR- INTx-
    Latency: 32
    Interrupt: pin A routed to IRQ 16
    Region 0: Memory at fbbff000 (32-bit, non-prefetchable) [size=4K]
    Region 1: I/O ports at be00 [size=256]
    Capabilities: [40] Power Management version 2
        Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA 
PME(D0-,D1-,D2-,D3hot+,D3cold+)
        Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
    Kernel driver in use: serial
00: b9 10 5a 54 07 00 90 02 00 00 03 07 00 20 00 00
10: 00 f0 bf fb 01 be 00 00 00 00 00 00 00 00 00 00
20: 00 00 00 00 00 00 00 00 00 00 00 00 20 20 5a 54
30: 00 00 00 00 40 00 00 00 00 00 00 00 0b 01 00 00

   Eli

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Web: http://www.billauer.co.il

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Messages in current thread:
open() on /dev/tty takes 30 seconds on 2.6.36, Eli Billauer, (Sat Oct 30, 12:47 am)
Re: open() on /dev/tty takes 30 seconds on 2.6.36, Andrew Morton, (Sat Oct 30, 11:46 am)
Re: open() on /dev/tty takes 30 seconds on 2.6.36, Arnd Bergmann, (Sat Oct 30, 1:46 pm)
Re: open() on /dev/tty takes 30 seconds on 2.6.36, Eli Billauer, (Sat Oct 30, 5:20 pm)
Re: open() on /dev/tty takes 30 seconds on 2.6.36, Arnd Bergmann, (Sat Oct 30, 8:36 pm)
Re: open() on /dev/tty takes 30 seconds on 2.6.36, James Cloos, (Sat Oct 30, 11:34 pm)
Re: open() on /dev/tty takes 30 seconds on 2.6.36, Arnd Bergmann, (Sun Oct 31, 4:36 am)
Re: open() on /dev/tty takes 30 seconds on 2.6.36, Eli Billauer, (Sun Oct 31, 6:12 pm)
Re: open() on /dev/tty takes 30 seconds on 2.6.36, Arnd Bergmann, (Mon Nov 1, 12:39 pm)
Re: open() on /dev/tty takes 30 seconds on 2.6.36, Tejun Heo, (Tue Nov 2, 3:28 am)
Re: open() on /dev/tty takes 30 seconds on 2.6.36, Eli Billauer, (Tue Nov 2, 5:15 pm)
Re: open() on /dev/tty takes 30 seconds on 2.6.36, Arnd Bergmann, (Tue Nov 2, 8:32 pm)