Ending strace on a process causes hung network connection

[Yong Huang]

This may be Oracle specific. I have Oracle 11gR2 installed on RHEL 5.3 (kernel 2.6.18-92.1.22.el5, x86 64-bit). From client, I can run tnsping to do the basic Oracle SQL*Net connection test, and can use sqlplus to connect into Oracle through SQL*Net, even while I'm running strace -p <TNS listener> on the server. But if I press Control-C to end strace on the server, tnsping or sqlplus hangs. It's reproducible.

When the listener does not hang, `telnet <listener IP> 1521' (1521 is the listener port number) allows you to type a few (4?) keystrokes and you're back to your own prompt (unless you happen to send a message according to the undocumented SQL*Net protocol). But when it hangs, telnet to it and you can type anything and it never closes the connection.

Question: What could cause strace to have this disruptive effect on a running process?

Yong Huang