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    SubjectRE: 2.6.9: serial_core: uart_open
    > -----Original Message-----
    > From: Russell King
    > Sent: Thursday, July 14, 2005 11:57 AM
    > To: karl malbrain
    > Cc: Linux-Kernel@Vger. Kernel. Org
    > Subject: Re: 2.6.9: serial_core: uart_open
    > On Thu, Jul 14, 2005 at 10:16:23AM -0700, karl malbrain wrote:
    > > I'd love to do a ps listing for you, but, except for the mouse,
    > the system
    > > is completely unresponsive after issuing the blocking open("/dev/ttyS1",
    > > O_RDRW).
    > >
    > > Telnet is dead; the console will respond to the mouse, but the
    > only thing I
    > > can do is close the xterm window and thereby kill the process.
    > I can launch
    > > a new xterm window from the menu using the mouse, but the new
    > window is dead
    > > and has no cursor nor bash prompt.
    > >
    > > The clock on the display is being updated. After several hours
    > the system
    > > reboots on its own.
    > >
    > > I recall from my DOS days that 8250/16550 programming requires that the
    > > specific IIR source be responded to, or the chip will immediately
    > > turn-around with another interrupt. It doesn't look like 8250.c is
    > > organized to respond directly to the modem-status-change value
    > in IIR which
    > > requires reading MSR to reset.
    > Well, at this point interrupts are enabled, and _are_ handled. The
    > only thing we use the IIR for is to answer the question "did this
    > device say it had an interrupt?"
    > If it did, we unconditionally read the MSR without fail.
    > So, I've no idea what so ever about what's going on here. I don't
    > understand why your system is behaving the way it is. Therefore,
    > I don't think we can progress this any further, sorry.


    The problem is that ALL SYSTEM CALLS to open "/dev/tty" are blocking!! even
    with O_NDELAY set and even from completely disjoint sessions. I discovered
    this via issuing "strace sh". That's why the new xterm windows froze.

    The original process doing the open("/dev/ttyS1", O_RDWR) is listed in the
    ps aux listing as status S+.

    Hope this helps.... karl m

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