316b656326
Prior to this commit, in configurations using the alternate SysTick clocking, vPortSuppressTicksAndSleep() might cause xTickCount to jump ahead as much as the entire expected idle time or fall behind as much as one full tick compared to time as measured by the SysTick. SysTick ------- The SysTick is the hardware timer that provides the OS tick interrupt in the official ports for Cortex M. SysTick starts counting down from the value stored in its reload register. When SysTick reaches zero, it requests an interrupt. On the next SysTick clock cycle, it loads the counter again from the reload register. The SysTick has a configuration option to be clocked by an alternate clock besides the core clock. This alternate clock is MCU dependent. Scenarios Fixed --------------- The new code in this commit handles the following scenarios that were not handled correctly prior to this commit. 1. Before the sleep, vPortSuppressTicksAndSleep() stops the SysTick on zero, long after SysTick reached zero. Prior to this commit, this scenario caused xTickCount to jump ahead one full tick for the same reason documented here: https://github.com/FreeRTOS/FreeRTOS-Kernel/pull/59/commits/0c7b04bd3a745c52151abebc882eed3f811c4c81 2. After the sleep, vPortSuppressTicksAndSleep() stops the SysTick before it loads the counter from the reload register. Prior to this commit, this scenario caused xTickCount to jump ahead by the entire expected idle time (xExpectedIdleTime) because the current-count register is zero before it loads from the reload register. 3. Prior to return, vPortSuppressTicksAndSleep() attempts to start a short SysTick period when the current SysTick clock cycle has a lot of time remaining. Prior to this commit, this scenario could cause xTickCount to fall behind by as much as nearly one full tick because the short SysTick cycle never started. Note that #3 is partially fixed by https://github.com/FreeRTOS/FreeRTOS-Kernel/pull/59/commits/967acc9b200d3d4beeb289d9da9e88798074b431 even though that commit addresses a different issue. So this commit completes the partial fix. |
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|---|---|---|
| .github | ||
| include | ||
| portable | ||
| CONTRIBUTING.md | ||
| croutine.c | ||
| event_groups.c | ||
| GitHub-FreeRTOS-Kernel-Home.url | ||
| History.txt | ||
| LICENSE.md | ||
| list.c | ||
| queue.c | ||
| Quick_Start_Guide.url | ||
| README.md | ||
| SECURITY.md | ||
| stream_buffer.c | ||
| tasks.c | ||
| timers.c | ||
Getting started
This repository contains FreeRTOS kernel source/header files and kernel ports only. This repository is referenced as a submodule in FreeRTOS/FreeRTOS repository, which contains pre-configured demo application projects under FreeRTOS/Demo directory.
The easiest way to use FreeRTOS is to start with one of the pre-configured demo application projects. That way you will have the correct FreeRTOS source files included, and the correct include paths configured. Once a demo application is building and executing you can remove the demo application files, and start to add in your own application source files. See the FreeRTOS Kernel Quick Start Guide for detailed instructions and other useful links.
Additionally, for FreeRTOS kernel feature information refer to the Developer Documentation, and API Reference.
Getting help
If you have any questions or need assistance troubleshooting your FreeRTOS project, we have an active community that can help on the FreeRTOS Community Support Forum.
Cloning this repository
To clone using HTTPS:
git clone https://github.com/FreeRTOS/FreeRTOS-Kernel.git
Using SSH:
git clone git@github.com:FreeRTOS/FreeRTOS-Kernel.git
Repository structure
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The root of this repository contains the three files that are common to every port - list.c, queue.c and tasks.c. The kernel is contained within these three files. croutine.c implements the optional co-routine functionality - which is normally only used on very memory limited systems.
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The
./portabledirectory contains the files that are specific to a particular microcontroller and/or compiler. See the readme file in the./portabledirectory for more information. -
The
./includedirectory contains the real time kernel header files.