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The introduction of `portMEMORY_BARRIER` will ensure the places in the kernel use a barrier will work. For example, `xTaskResumeAll` has a memory barrier to ensure its correctness when compiled with optimization enabled. Without the barrier `xTaskResumeAll` can fail (e.g. start reading and writing to address 0 and/or infinite looping) when `xPendingReadyList` contains more than one task to restore. In `xTaskResumeAll` the compiler chooses to cache the `pxTCB` the first time through the loop for use in every subsequent loop. This is incorrect as the removal of `pxTCB->xEventListItem` will actually change the value of `pxTCB` if it was read again at the top of the loop. The barrier forces the compiler to read `pxTCB` again at the top of the loop. The compiler is operating correctly. The removal `pxTCB->xEventListItem` executes on a `List_t *` and `ListItem_t *`. This means that the compiler can assume that any `MiniListItem_t` values are unchanged by the loop (i.e. "strict-aliasing"). This allows the compiler to cache `pxTCB` as it is obtained via a `MiniListItem_t`. This is incorrect in this case because it is possible for a `ListItem_t *` to actually alias a `MiniListItem_t`. This is technically a "violation of aliasing rules" so we use the the barrier to disable the strict-aliasing optimization in this loop. |
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| .. | ||
| ARMClang | ||
| ARMv8M | ||
| BCC/16BitDOS | ||
| CCS | ||
| CodeWarrior | ||
| Common | ||
| GCC | ||
| IAR | ||
| Keil | ||
| MemMang | ||
| MikroC/ARM_CM4F | ||
| MPLAB | ||
| MSVC-MingW | ||
| oWatcom/16BitDOS | ||
| Paradigm/Tern_EE | ||
| Renesas | ||
| Rowley | ||
| RVDS | ||
| SDCC/Cygnal | ||
| Softune | ||
| Tasking/ARM_CM4F | ||
| ThirdParty | ||
| WizC/PIC18 | ||
| CMakeLists.txt | ||
| readme.txt | ||
Each real time kernel port consists of three files that contain the core kernel components and are common to every port, and one or more files that are specific to a particular microcontroller and/or compiler. + The FreeRTOS/Source/Portable/MemMang directory contains the five sample memory allocators as described on the https://www.FreeRTOS.org WEB site. + The other directories each contain files specific to a particular microcontroller or compiler, where the directory name denotes the compiler specific files the directory contains. For example, if you are interested in the [compiler] port for the [architecture] microcontroller, then the port specific files are contained in FreeRTOS/Source/Portable/[compiler]/[architecture] directory. If this is the only port you are interested in then all the other directories can be ignored.