messagemode named pipes investigation: blocking-reads block writers indefinitely

[Luke Kenneth Casson Leighton]

fascinatingly strange observation came out of writing the latest test
(threadwrites) to do namedpipe interoperability testing.

main process: blocking-read on namedpipe.
5 threads: write to same named pipe

the writes NEVER return (this is with xp).

so that WOULD indicate that there IS a per-pipe mutex (and that there
are bugs in nt!)

l.

messagemode named pipes investigation: blocking-reads block writers indefinitely

[Luke Kenneth Casson Leighton]

> main process: blocking-read on namedpipe.
> 5 threads: write to same named pipe
>
> the writes NEVER return (this is with xp).
>
> so that WOULD indicate that there IS a per-pipe mutex (and that there
> are bugs in nt!)

unbelievable.

 turns out it's an msvcrt bug (in windows nt).  if you use
_beginthread() to create the 5 threads (or even just the one), the
reader can block the writer(s).  however if you use CreateThread(),
everything's hunky-dory.

 anyone want to record _that_ one as a future interoperability
bug-test, be my guest! ha ha :)  no, but seriously: if someone tells
me it's a worthwhile thing to have as an interoperability test, i'll
write one.

l.