Console in multi-thread environment

[Rafael Zingler]

Hi,

I´ve doubts about the console widget with in a project that uses FreeRTOS. There are calls to the gwinPrintf() function in more than one thread. When this function is called from a timer callback function and simultaneously in other thread, the console´s content is jumbled. Sometimes, even the characters are not correctly redrawn in such case.

Is this behavior expected?

Thanks.

Edited March 21, 2017 by Rafael Zingler

[Joel Bodenmann]

Hello Rafael,

The characters being drawn incorrectly in the screen indicates that you didn't set GDISP_NEED_MULTITHREAD to TRUE which will make the entire GDISP API become thread safe.
The GWIN console widget itself is however not multi-thread safe so you have to protect access to it yourself. The solution depends on your application. You can either go with a classic producer/consumer where you have just one consumer (the sole thread that writes to the console) and multiple producers. Alternatively you can simply use the a mutex to protect access inside your application.
Note that we strongly recommend using the µGFX high-level API such as gfxMutexCreate() and similar to keep your application portable. They are simple wrappers (often just macros so no overhead) towards the corresponding FreeRTOS mutex API.

I hope that helps.

[Rafael Zingler]

Thanks, Joel.

 

The GDISP_NEED_MULTITHREAD option is already configured as TRUE in the gfxconf.h file.

For now, to solve the problem, I´ll implement the consumer/producer scheme to guarantee "serial" access to the console, with only the consumer accessing this widget. I´m going to replace, then, the gwinPrintf () calls with xQueueSend() calls, to send the desired messages to the console.

Thanks.

Edited March 21, 2017 by Rafael Zingler

[inmarket]

Jumbled text may be expected but characters not being drawn correctly is definitely not.

Characters are drawn by the gdisp layer either one by one or as a string. If GDISP_NEED_MULTITHREAD is TRUE is should be impossible to get character corruption.

Please check carefully exactly what is happenning.

[Joel Bodenmann]

Agreed. If the characters themselves are not being drawn then there's something very wrong. Don't forget to make a clean-build if you changed something in the configuration file.