Uncaught exceptions can cause node to hang

[bminer]

In certain situations, process.exit(1) or an uncaught exception will cause the Node.js process to hang when using node-serialport. The desired behavior is for the Node process to die. Instead, the process remains open and just hangs.

I am working on some reproducible code to demonstrate this bug. I am fairly certain that node-serialport is the culprit... it reminds me of issue #150.

This problem occurs on node-serialport 1.2.5. Node 0.10.22. Debian Linux 7.0

[bminer]

Update: I have narrowed the problem to an issue with the getaddrinfo system call (see related issue nodejs/node-v0.x-archive#2868). When dns.lookup fails due to a network connectivity problem, there are long delays reading the serial port. Eventually, the getaddrinfo system call returns the ENOTFOUND error, and then Node hangs.

Why node-serialport causes this hang-up... I still don't know. But, it's probably related to getaddrinfo sharing the thread pool with node-serialport.

Very interesting and strange...

[ruswerner]

I also have this problem. I'm running on Rasbian kernel 3.10.24+, node v0.10.12. I like to resume stdin and then listen for the 'SIGINT' event on process. Then I cleanup open ports and other application stuff,and explicitly call process.exit(). If I call serialPort.close() in my SIGINT handler, then try to call process.exit(), it just hangs. I have to ctrl-Z and kill -9 node to recover.

This is really annoying, because I would like to call process.exit() in the serial.close() callback function to ensure everything is closed properly, but it just hangs.

So at this point, I just don't close the serial port. It seems to be fine; I'm just using the /dev/ttyAMA0 (rx/tx pins) on the rpi to talk to an arduino.

Anyone have any more info on this?

[JayBeavers]

What a fascinating bug, great sleuthing @bminer! Do you have a recommended fix and if so could you submit a pull request?

[bminer]

@JayBeavers - Unfortunately, I do not have a fix at this time. It's also pretty tough to reproduce the problem. (sigh)

If I find any more information, I will post back here.

[voodootikigod]

@bminer any update or data?

[bminer]

Sadly, no. I do not have time ATM to debug this issue. However, I can say that libuv is working on separating the thread pools for different tasks (libuv/leps#4). And, they are working on an approach to allow reading from TTY/serial ports (libuv/libuv#19). So, eventually, these wonderful things will make it to Node.js.

In the meantime, I have been using node-serialport and other libs to address the issue, and I just deal with the bugs.

[reconbot]

We've had a lot of similar bugs fixed as well as some major rewrites of our c++ code since this bug was filed. I sure hope we caught this bug, but since it was never quite identified, I'm closing this issue.

[bminer]

Sounds good, thanks. I'm not sure if it's still an issue or not either. I've been pretty happy with the stability improvements made to this lib.