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Q98416: DosOpen Thread Blocked Pending DosWaitNmPipe

Article: Q98416
Product(s): Microsoft LAN Manager
Version(s): 
Operating System(s): 
Keyword(s): 
Last Modified: 30-JUL-2001

SUMMARY
=======

DosOpen() local call threads become blocked if a remote pipe does not open
pending a DosWaitNmPipe() in a different thread. This is by design in OS/2 and
is easily worked around.

MORE INFORMATION
================

Set the ulTIMEOUT parameter of DosWaitNmPipe to a small value that is an
acceptable postponement for other I/O--maybe 2 seconds--then put the
DosWaitNmPipe in a loop. The DosWaitNmPipe now, in effect, "waits forever"
(unless you want to limit the loop instance), but every 2 seconds other I/O from
threads within the same process are serviced.

OS/2 serializes I/O at the process level, which creates (essentially) a queue of
I/O requests per process. If two threads within the same process issue I/O calls
to the operating system, the first one (longest time in queue) becomes the
DosWaitNmPipe, and the second becomes the DosOpen. The operating system must
complete processing the DosWaitNmPipe before it can entertain the DosOpen.

This behavior is not present in NT, as NT serializes I/O per thread, not per
process.

Additional query words: 2.10 2.1 2.10a 2.1a 2.20 2.2

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