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pigweed / third_party / github / FreeRTOS / FreeRTOS-Kernel / 30283b57dfd23f017389f0cfaf9318f7f2469027
commit30283b57dfd23f017389f0cfaf9318f7f2469027[log] [tgz]
authorRahul Kar <118818625+kar-rahul-aws@users.noreply.github.com>Tue Oct 17 15:05:18 2023 +0530
committerGitHub <noreply@github.com>Tue Oct 17 15:05:18 2023 +0530
treef992ac4346850e7965a53c4c68e5e5bd84bdbb5c
parent7ffc6a74655ec8a53fdc28fa1cccc74c1c747ecd [diff]
Fix xTaskNotifyWait & ulTaskNotifyTake determinism. (#833)

This PR fixes the bug described in the following issue:
https://github.com/FreeRTOS/FreeRTOS-Kernel/issues/612.
This was originally contributed in the following PR:
https://github.com/FreeRTOS/FreeRTOS-Kernel/pull/625.

The implementation suspends the scheduler before exiting the
critical section (i.e. before enabling interrupts). If we do not do
so, a notification sent from an ISR, which happens after exiting
the critical section and before suspending the scheduler, will
get lost. The sequence of events will be:

1. Exit critical section.
2. Interrupt - ISR calls xTaskNotifyFromISR which adds the task to
    the Ready list.
3. Suspend scheduler.
4. prvAddCurrentTaskToDelayedList moves the task to the delayed
    or suspended list.
5. Resume scheduler does not touch the task (because it is not on
    the pendingReady list), effectively losing the notification from
    the ISR.

The same does not happen when we suspend the scheduler before
exiting the critical section. The sequence of events in this case will
be:

1. Suspend scheduler.
2. Exit critical section.
3. Interrupt - ISR calls xTaskNotifyFromISR which adds the task to
    the pendingReady list as the scheduler is suspended.
4. prvAddCurrentTaskToDelayedList adds the task to delayed or
    suspended list. Note that this operation does not nullify the add
    to pendingReady list done in the above step because a different
    list item, namely xEventListItem, is used for adding the task to the
    pendingReady list. In other words, the task still remains on the
    pendingReady list.
5. Resume scheduler moves the task from pendingReady list to the Ready list.

------------

Co-authored-by: Jacob Carver <karver8@github.com>
1 file changed
tree: f992ac4346850e7965a53c4c68e5e5bd84bdbb5c
  1. .github/
  2. cmake_example/
  3. include/
  4. portable/
  5. sample_configuration/
  6. .git-blame-ignore-revs
  7. .gitattributes
  8. .gitmodules
  9. CMakeLists.txt
  10. croutine.c
  11. cspell.config.yaml
  12. event_groups.c
  13. GitHub-FreeRTOS-Kernel-Home.url
  14. History.txt
  15. LICENSE.md
  16. list.c
  17. manifest.yml
  18. MISRA.md
  19. queue.c
  20. Quick_Start_Guide.url
  21. README.md
  22. stream_buffer.c
  23. tasks.c
  24. timers.c
README.md

CMock Unit Tests codecov

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.

Also for contributing and creating a Pull Request please refer to the instructions here.

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.

To consume FreeRTOS-Kernel

Consume with CMake

If using CMake, it is recommended to use this repository using FetchContent. Add the following into your project‘s main or a subdirectory’s CMakeLists.txt:

  • Define the source and version/tag you want to use:
FetchContent_Declare( freertos_kernel
  GIT_REPOSITORY https://github.com/FreeRTOS/FreeRTOS-Kernel.git
  GIT_TAG        main #Note: Best practice to use specific git-hash or tagged version
)

In case you prefer to add it as a git submodule, do:

git submodule add https://github.com/FreeRTOS/FreeRTOS-Kernel.git <path of the submodule>
git submodule update --init
  • Add a freertos_config library (typically an INTERFACE library) The following assumes the directory structure:
    • include/FreeRTOSConfig.h
add_library(freertos_config INTERFACE)

target_include_directories(freertos_config SYSTEM
INTERFACE
    include
)

target_compile_definitions(freertos_config
  INTERFACE
    projCOVERAGE_TEST=0
)

In case you installed FreeRTOS-Kernel as a submodule, you will have to add it as a subdirectory:

add_subdirectory(${FREERTOS_PATH})
  • Configure the FreeRTOS-Kernel and make it available
    • this particular example supports a native and cross-compiled build option.
set( FREERTOS_HEAP "4" CACHE STRING "" FORCE)
# Select the native compile PORT
set( FREERTOS_PORT "GCC_POSIX" CACHE STRING "" FORCE)
# Select the cross-compile PORT
if (CMAKE_CROSSCOMPILING)
  set(FREERTOS_PORT "GCC_ARM_CA9" CACHE STRING "" FORCE)
endif()

FetchContent_MakeAvailable(freertos_kernel)
  • In case of cross compilation, you should also add the following to freertos_config:
target_compile_definitions(freertos_config INTERFACE ${definitions})
target_compile_options(freertos_config INTERFACE ${options})

Consuming stand-alone - 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

  • 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.

  • The ./portable directory contains the files that are specific to a particular microcontroller and/or compiler. See the readme file in the ./portable directory for more information.

  • The ./include directory contains the real time kernel header files.

  • The ./sample_configuration directory contains a sample FreeRTOSConfig.h to help jumpstart a new project. See the FreeRTOSConfig.h file for instructions.

Code Formatting

FreeRTOS files are formatted using the “uncrustify” tool. The configuration file used by uncrustify can be found in the FreeRTOS/CI-CD-GitHub-Actions's uncrustify.cfg file.

Line Endings

File checked into the FreeRTOS-Kernel repository use unix-style LF line endings for the best compatibility with git.

For optimal compatibility with Microsoft Windows tools, it is best to enable the git autocrlf feature. You can enable this setting for the current repository using the following command:

git config core.autocrlf true

Git History Optimizations

Some commits in this repository perform large refactors which touch many lines and lead to unwanted behavior when using the git blame command. You can configure git to ignore the list of large refactor commits in this repository with the following command:

git config blame.ignoreRevsFile .git-blame-ignore-revs

Spelling and Formatting

We recommend using Visual Studio Code, commonly referred to as VSCode, when working on the FreeRTOS-Kernel. The FreeRTOS-Kernel also uses cSpell as part of its spelling check. The config file for which can be found at cspell.config.yaml There is additionally a cSpell plugin for VSCode that can be used as well. .cSpellWords.txt contains words that are not traditionally found in an English dictionary. It is used by the spellchecker to verify the various jargon, variable names, and other odd words used in the FreeRTOS code base are correct. If your pull request fails to pass the spelling and you believe this is a mistake, then add the word to .cSpellWords.txt. When adding a word please then sort the list, which can be done by running the bash command: sort -u .cSpellWords.txt -o .cSpellWords.txt Note that only the FreeRTOS-Kernel Source Files, include, portable/MemMang, and portable/Common files are checked for proper spelling, and formatting at this time.