uclibc(1.0.12) mq_send return value and errno issue

Frank Liu fliu at universalbiosensors.com
Fri Nov 18 03:43:45 UTC 2016


Hi All,

Kernel version : 4.4.19-linux4sam_5.4
uclibc version : 1.0.12
uclibc threading support : NPTL
Processor Arch: ARM

We create a NONBLOCKING message queue.

The expected behavior is when the message queue is full, calling mq_send would return -1 and set errno to EAGAIN(11). However we are seeing some inconsistent behaviors of mq_send.

When calling mq_send in a single threaded environment, the expected behavior is observed.

If the program starts a second thread, which is doing completely different task, calling mq_send when the queue is full would return -11 instead of -1. Also, the errno is set to an incorrect value. Values we have seen are 0, 2, which are completely different from the expected EAGAIN(11).

Frank

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