Help: Killing TIOCMIWAIT ioctl threads

[David Baron <d_baron@012.net.il>]

I have a program to control a speakerphone modem. One thread monitors for 
rings, based on xringd code, using an icotl TIOCMIWAIT. This uses one file 
descriptor number to the modem /dev and runs in the background. Other threads 
open of the modem for write access and send sequences to answer the call or 
dial a call, etc.Program is using qt4, written as a plasma applet.

Problem is that xringd thread never ends. Closing the plasmoid viewer or 
otherwize removing it leaves this thread running even after its QThread object 
has been destroyed. Not very well behaved at all. So after several sessions of 
testing, the modem is borked and nothing can access it, not even minicom. One 
can open the /dev but nothing more.

Raising signals as set up in xringd has no effect. Only an outright kill of 
the whole thing MAY (no destroyed while running message anyway) stop it. NO 
answers to this on Google.

The man pages for these calls show some possibilities that could be tried from 
the applet's destructor.:
1. Insert a character into the read buffer that generates the signal? There 
are a whole series of these, one for each signal. However, simply raising the 
signal did not work.
2. Do an ioctl to set the ring bit. Before this I could set an abort flag and 
end the run at this point?

Note that this program uses two file numbers, one for the read-only xringd 
thread and one for any operations that need write access. If there were a way 
to turn write access on and off, one descriptor number would suffice. Keeping 
things read-only until I want to take action keeps the program from 
interfering with getty operations and such if the user uses them. Getty can 
answer the call if the user does not do so from the program after n rings, for 
example. That's how xringd does it.