Concurrency issues?

[dvader]

I used to get crashes when logging "conn_open(): error in accept()", in particular, the call strerror(errno) crashes. After some reading it seems strerr is not re-entrant safe http://stackoverflow.com/questions/900338/why-cant-i-use-strerror. I am not sure if re-entrancy is the cause of the crash but after removing the function call and logging only errno, the software doesn't crash anymore.

However, it still sometimes get the error:
1485184829:392664 conn_open(): error in accept() (11)
1485184829:413938 tty: error in read() (11)
and sometimes only the accept error without the tty error.
I'll get the error more often if I use two clients to make requests.

I wonder if this error is caused by re-entrancy issues? Maybe there is a need to put mutexes on some function calls to make them thread safe?

[dvader]

I also recently got the following error:
1485184870:634270 conn[192.168.2.51]: state CONN_TTY deadlock.

[3cky]

Hmm, thanks for reporting. Since mbusd is single-threaded application, re-entrancy shouldn't be an issue. I will look into it, but could you provide some context? What OS and hardware are you using (especially tty), also some info about client app and typical requests pattern.

[dvader]

Linux 2.4.21-rmk1 #1 Mon Mar 5 15:00:39 CET 2012 armv4l unknown
Cirrus Logic ARM EP7312-CBZ http://ca.mouser.com/ProductDetail/Cirrus-Logic/EP7312-CBZ/?qs=bUPhaerQQeGSZ7MA5Dwd%2FA%3D%3D
I am not using RxTx control, it's a full duplex UART.
I am using qModmaster https://sourceforge.net/projects/qmodmaster/ as a client and I am running two of them with 123 register request every second.
Here's a sample request and response:
INFO 2017-02-17T16:33:33.685 ..\qModMaster\src\modbusadapter.cpp @ 379 Rx Data : "26 73 00 00 00 f9 01 03 f6 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0d 00 02 00 00 00 00 00 02 00 11 00 11 00 10 00 22 00 18 00 c0 00 a8 00 02 00 3b 00 ff 00 ff 00 00 00 00 00 c0 00 a8 00 02 00 33 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 "
INFO 2017-02-17T16:33:33.685 ..\qModMaster\src\modbusadapter.cpp @ 226 Modbus Read Data return value = 123
INFO 2017-02-17T16:33:33.685 ..\qModMaster\src\mainwindow.cpp @ 543 Packets sent / received = 9843 , errors = 4
INFO 2017-02-17T16:33:34.574 ..\qModMaster\src\modbusadapter.cpp @ 161 Modbus Transaction. Function Code = 3
INFO 2017-02-17T16:33:34.574 ..\qModMaster\src\modbusadapter.cpp @ 190 Modbus Read Data
INFO 2017-02-17T16:33:34.574 ..\qModMaster\src\modbusadapter.cpp @ 360 Tx Data : "26 74 00 00 00 06 01 03 13 ec 00 7b "
INFO 2017-02-17T16:33:34.761 ..\qModMaster\src\modbusadapter.cpp @ 379 Rx Data : "26 74 00 00 00 f9 01 03 f6 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0d 00 02 00 00 00 00 00 02 00 11 00 11 00 10 00 22 00 19 00 c0 00 a8 00 02 00 3b 00 ff 00 ff 00 00 00 00 00 c0 00 a8 00 02 00 33 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 "
INFO 2017-02-17T16:33:34.761 ..\qModMaster\src\modbusadapter.cpp @ 226 Modbus Read Data return value = 123
INFO 2017-02-17T16:33:34.761 ..\qModMaster\src\mainwindow.cpp @ 543 Packets sent / received = 9844 , errors = 4

[nickma82]

@dvader any updates on that?

[nickma82]

@3cky plz close that ticket