The problem does not lie in the CRT. This does everything that my sample in the OP and your sample do, using the CRT directly, and there are no signs of any locking:

<Reveal this spoiler or all in this thread>

Output:

C:\test>828831.exe
828831.c(115):_fstat( lsn, &s ) == -1
        failed with error 9 (Bad file descriptor)
828831.c(116):_tell( lsn )
        failed with error 9 (Bad file descriptor)
828831.c(117):_dup( lsn ) == -1
        failed with error 9 (Bad file descriptor)
Connect from: 120
Thread started for client 120
Connect from: 128
Thread started for client 128
Thread completed 4895 echos for client 128
Thread completed 11575 echos for client 120

[download]

The locking is occuring within Perl itself, but damned if I can work out where. It must be in Win32 specific code given that other OSs aren't suffering the same problem. But given that OS conditional code is spread throughout the entire code base, it'll take someone clever than me to find it.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
"I'd rather go naked than blow up my ass"

In reply to Re^10: threads + sockets stalling question by BrowserUk
in thread threads + sockets stalling question by BrowserUk

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