clintp has asked for the wisdom of the Perl Monks concerning the following question:
At this url (bundle.tar, 39K) is a cut-down version of the problem. Too much code to post, I'll give an walkthrough on creating the bug momentarily.
The problem is this: I've got multiple incoming sockets (IO::Socket::INET) that I'm managing I/O using select (IO::Select), when I have the listening program call Win32::Process::Create all of the *already established* sockets stop working. They don't report an error, it's just that select() on them stops working. It doesn't seem to matter what the program Win32::Process:Create calls actually does (the .exe included is a "Hello, world") it always causes this.
From what I've read, the third flag to W:P:C is supposed to control file descriptor inheritance by children, but I can't get it to work one way or the other and it may not even be the problem. If this were Unix, it'd feel like a child-closing-parent's-descriptors problem but I'm not entirely sure how Win32 is handling all of this.
So to re-create the bug, do this:
- Unpack the tar bundle noted above.
- Start the program "testcase.pl". It's going to create "logfile" and update it as it goes along. No other output from "testcase.pl" is really important...
- Start a "tail -f logfile" or the equivalent for your OS and toolset. This is what to watch.
- Start a copy of "logstuff.pl". This will continually send stuff over an open socket to testcase.pl, which you can watch in the logfile.
- Once that's going, wait a few seconds and start "client.pl". This will send a 1-time request to testcase.pl to call an external program. (It'll probably report an "Err: No output", don't sweat it.)
If you start multiple logstuff.pl instances, this doesn't happen. They can connect, disconnect, etc... without problem.
And once testcase.pl has (buggily) dropped all of the other incoming sockets, re-establishing new connections work fine. The prior ones are still ignored however.
If anyone knows the reason for this nonsense between select()/W:P:C I'd love to know the answer. I've searched the newsgroups and documentation and I'm resonably sure there's not an obvious answer. And I don't *think* I've got a bug in my code because I've marked everywhere I'm opening/closing/reading/writing sockets and I'm sure I haven't accidentally killed something.
Thank you for your time!
PS: Keep your style nits to yourself, remember this is a stripped down/test case version of something much larger.
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Re: Win32::Process::Create and IO::Select bad interaction (SetHandleInformation)
by tye (Sage) on Jan 09, 2003 at 16:59 UTC
Re: Win32::Process::Create and IO::Select bad interaction
by clintp (Curate) on Jan 09, 2003 at 18:22 UTC