Quality RTOS & Embedded Software

 Real time embedded FreeRTOS RSS feed 
Real time embedded FreeRTOS mailing list 
Quick Start Supported MCUs PDF Books Trace Tools Ecosystem TCP & FAT Training




Loading

Desinherit after different mutex is given

Posted by Benjamin Meier on April 10, 2013
Hi all,

whilst analyzing my software i found something that concerned me.
I was wondering why the priority of the control-task is set back at this point in time.
But first things first.

The image below shows a part of a trace captured with percepio. There are no events hidden.
There are mainly three active tasks.
- Display (Priority 1)
- Radio (Priority 2)
- Control (Priority 3)

To share some resources with tasks (some were not active during the capture) there are mainly two mutexes:
- SPI Mutex
- Radio Mutex

Any task communicating with the display has to have the SPI mutex first.
Any task communicating with the radio needs to get the Radio mutex and then the SPI mutex.

Even though it isn't very pretty the control-task attempts to get the Radio-mutex and blocks.
This leads to the inheritance of the priority of the Radio-task, which has the radio mutex during the whole capture.

Somewhat later the priority of the radio-task is returned to its original priority (2).
This right after the radio-task returns the other mutex (SPI).

I cannot see any reason why this should be. The Radio-mutex is still owned by the radio-task.



Thanks for any idea, I'm quite confused right now...

RE: Desinherit after different mutex is given

Posted by Benjamin Meier on April 10, 2013
Also should to my opinion the control-task get active if the priority of the radio task was actually returned to 2.

RE: Desinherit after different mutex is given

Posted by Richard on April 10, 2013
The priority inheritance mechanism is very simply and does not stack inherited priorities - it assumes only one mutex is held at a time.

Regards.


[ Back to the top ]    [ About FreeRTOS ]    [ Sitemap ]    [ ]




Copyright (C) 2004-2010 Richard Barry. Copyright (C) 2010-2016 Real Time Engineers Ltd.
Any and all data, files, source code, html content and documentation included in the FreeRTOSTM distribution or available on this site are the exclusive property of Real Time Engineers Ltd.. See the files license.txt (included in the distribution) and this copyright notice for more information. FreeRTOSTM and FreeRTOS.orgTM are trade marks of Real Time Engineers Ltd.

Latest News:

FreeRTOS V9.0.0 is now available for download.


Free TCP/IP and file system demos for the RTOS


Sponsored Links

⇓ Now With No Code Size Limit! ⇓
⇑ Free Download Without Registering ⇑


FreeRTOS Partners

ARM Connected RTOS partner for all ARM microcontroller cores

Renesas Electronics Gold Alliance RTOS Partner.jpg

Microchip Premier RTOS Partner

RTOS partner of NXP for all NXP ARM microcontrollers

Atmel RTOS partner supporting ARM Cortex-M3 and AVR32 microcontrollers

STMicro RTOS partner supporting ARM7, ARM Cortex-M3, ARM Cortex-M4 and ARM Cortex-M0

Xilinx Microblaze and Zynq partner

Silicon Labs low power RTOS partner

Altera RTOS partner for Nios II and Cortex-A9 SoC

Freescale Alliance RTOS Member supporting ARM and ColdFire microcontrollers

Infineon ARM Cortex-M microcontrollers

Texas Instruments MCU Developer Network RTOS partner for ARM and MSP430 microcontrollers

Cypress RTOS partner supporting ARM Cortex-M3

Fujitsu RTOS partner supporting ARM Cortex-M3 and FM3

Microsemi (previously Actel) RTOS partner supporting ARM Cortex-M3

Atollic Partner

IAR Partner

Keil ARM Partner

Embedded Artists