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SubjectRe: open() on /dev/tty takes 30 seconds on 2.6.36
Arnd Bergmann wrote:

> Ok, that's certainly modem-manager in the tty_release function, calling
> uart_close, which has this code:
>
> if (port->closing_wait != ASYNC_CLOSING_WAIT_NONE) {
> /*
> * hack: open-coded tty_wait_until_sent to avoid
> * recursive tty_lock
> */
> long timeout = msecs_to_jiffies(port->closing_wait);
> if (wait_event_interruptible_timeout(tty->write_wait,
> !tty_chars_in_buffer(tty), timeout) >= 0)
> __uart_wait_until_sent(uport, timeout);
> }
>
> port->closing_wait gets initialized to 30 seconds, which fits your
> symptom.
>
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 Maybe my version is outdated?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.

> What does "lspci -vvx" show about the
> port?
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

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



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