wakeup() race condition. (theory)

[Karl Denninger]

In article <602 at sysco> chapman at sco.COM (Brian Chapman) writes:
>
>BTW just in case anyone is wondering, SCO's serial driver
>does *NOT* call wakeup from it's level 7 interrupt routine.

BTW: Just in case anyone cares, the reason people are investigating
     alternate drivers for SCO Xenix and non-intelligent boards is that the
     "stock" driver provided, while quite adaptable (and possessed with good
     overall performance): 

	1) Has never managed to get bi-directional ports w/internal locking
	   working (ala: open "non modem" port, modem port is blocked, etc.
	   It's been described here and is done by many other firms; email
	   me for full details).  Thus we have to use brain-dead schemes which 
	   work (some of the time) like ungetty, and I have to deal with
	   customers (and our gear) that has deadlocked lines once in a while.

	2) Has a broken RTS flow control capability.

(No flames for the "non-standard" in RS232.  Broken in the above means the 
 Telebit won't talk to it when RTSFLOW is selected; you get low RTS and 
 that's all folks!)

This (and the inclusion of '286-compiled utilities!) is really the only 
"nasty" complaint I have had with your software in the year or so I've been 
running it.  Other minor complaints include locking discrepancies with the 
SVID, but we've worked around those (and they're addressed in 2.3, from what 
I hear).

If SCO would fix the serial driver problems, and offer a reasonably-
inexpensive (ie: not a $600 update-the-entire-system fix) way to get the 
fix (aka: the "fix disks" you guys do now) then the stock driver would be 
completely adaquate.  If you additionally enabled FIFOs if present on the 
UARTs you'd have a bombshell.

At present, the 2.2.x /386 serial support out of the box is only passable
without external augmentation (ie: smart board w/driver).  It appears that
some internal design decisions in the kernel make it more difficult to get
reasonable operation from drivers that must operate at high priority as
well; note though that I'm only a decent driver-hacker (as opposed to a guru).  We have had some interesting problems playing with replacements for the
stock stuff - _nothing_ is reliable enough for me to release yet (it's not
our code; but we're hacking on it).

We've not seen 2.3 yet; the last time I checked an update from 2.2.x was not
available, nor was cost of same, although I could obtain a "new" 2.3 (at
full cost, of course).

--
Karl Denninger (karl at ddsw1.MCS.COM, ddsw1!karl)
Data: [+1 312 566-8912], Voice: [+1 312 566-8910]
Macro Computer Solutions, Inc.    	"Quality solutions at a fair price"