Re: Managing the fork/execing and reaping of child processes

Perhaps not the issue, but ++$active_readers should be later in the parent, after checking if the fork was successful.

Why the exec in line 47? You could just as easily print from perl.

What system are you running on? I'm guessing there's a fork limit or something involved, and the perl script isn't getting any CPU or IO cycles, and is hanging there. Have you checked the CPU usage? Have you considered tracing the execution, and finding the last line executed before the hang?

-QM
--
Quantum Mechanics: The dreams stuff is made of

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Re^2: Managing the fork/execing and reaping of child processes by ibm1620 (Hermit) on Jul 16, 2015 at 15:53 UTC
In the real program, I exec a C program. I just wanted to keep differences to a minimum in this stripped-down version. I will look into the $active_readers question.	[reply]
Re^3: Managing the fork/execing and reaping of child processes by ibm1620 (Hermit) on Jul 16, 2015 at 16:00 UTC
System is CentOS. I don't know what kind of PID limits there are. When the freeze occurs, there's no CPU being used on the box (I'm the only occupant currently). There are no zombies. What are you referring to by "tracing"?	[reply]
Re^4: Managing the fork/execing and reaping of child processes by QM (Parson) on Jul 17, 2015 at 08:20 UTC
"Tracing" could be something as simple as sprinkling `print STDERR "This is line ", __LINE__, "\n"` [download] most everywhere, to using the debugger with actions on interesting lines, to one of the modules that wraps around the bytecode. -QM -- Quantum Mechanics: The dreams stuff is made of	[reply] [d/l]
Re^2: Managing the fork/execing and reaping of child processes by ibm1620 (Hermit) on Jul 16, 2015 at 16:04 UTC
Moving ++$active_readers didn't help (not surprisingly; if the fork were to fail, my program would exit).	[reply]