[DragonFlyBSD - Bug #3215] (New) Hang in tcdrain(3) after write(3)

bugtracker-admin at leaf.dragonflybsd.org bugtracker-admin at leaf.dragonflybsd.org
Mon Nov 25 15:08:41 PST 2019

Issue #3215 has been reported by noloader.

Bug #3215: Hang in tcdrain(3) after write(3)

* Author: noloader
* Status: New
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
Hi Everyone,

I'm testing some software on DragonFly. There's not much to it. It
talks to the modem. It sends an ATZ and reads the response. Linux,
FreeBSD, NetBSD, OpenBSD and OS X are OK.

For my test rig I have a USR5637 modem,
https://www.amazon.com/gp/product/B0013FDLM0. The modem is located at

DragonFly hangs on the call to tcdrain(3). Looking at the man page I
don't see any special handling. Cf.,

Attached is the reproducer. The trace is:

% ./test.exe
Getting tty
Setting tty options
Flushing tty
Setting tty
Writing ATZ
Waiting for write  <<-- call to tcdrain(fd)


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