uclibc(1.0.12) mq_send return value and errno issue

Frank Liu fliu at universalbiosensors.com
Fri Nov 18 06:45:53 UTC 2016


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 at uclibc-ng.org] 
Sent: Friday, November 18, 2016 5:13 PM
To: Frank Liu
Cc: 'uclibc at uclibc.org'; devel at uclibc-ng.org; Dushara Jayasinghe (dushara at 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
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