Please see the attached sample code.

If I turn READERS and WRITERS to 0, the test works fine.

Adding another thread in the process by setting a non-zero number to either READERS or WRITER, the test program crashes due to the assertion at line 99.

Regards

-----Original Message----- From: Waldemar Brodkorb [mailto:wbx@uclibc-ng.org] Sent: Friday, November 18, 2016 5:13 PM To: Frank Liu Cc: 'uclibc@uclibc.org'; devel@uclibc-ng.org; Dushara Jayasinghe (dushara@successful.com.au) Subject: Re: uclibc(1.0.12) mq_send return value and errno issue

Hi, Frank Liu wrote,

Hi All,

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

Better you switch to uClibc-ng mailinglist for this question.

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).

Can you provide a simple test case to check the behaviour?

best regards Waldemar