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.
* Add better pointer declaration readability
I revised the declaration of single-line pointers by splitting it into
multiple lines. Now, every pointer is declared (and initialized
accordingly) on its own line. This refactoring should enhance
readability and decrease the probability of error when a new pointer is
added/removed or a current one has its initialization value modified.
Signed-off-by: Cristian Cristea <cristiancristea00@gmail.com>
* Remove unnecessary whitespace characters and lines
It removes whitespace characters at the end of lines (empty or
othwerwise) and clear lines at the end of the file (only one remains).
It is an automatic operation done by git.
Signed-off-by: Cristian Cristea <cristiancristea00@gmail.com>
Signed-off-by: Cristian Cristea <cristiancristea00@gmail.com>
* Add xPortRemoveInterruptHandler API
This API is added to the MicroBlazeV9 port. It enables the application
writer to remove an interrupt handler.
This was originally contributed in this PR - https://github.com/FreeRTOS/FreeRTOS-Kernel/pull/523
* Change API signature to return void
This makes the API similar to vPortDisableInterrupt.
Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>
Co-authored-by: Gavin Lambert <uecasm@users.noreply.github.com>
* Style: Change FreeRTOS websites in comments
* Style: Change freertos to FreeRTOS in comments
* Style: Remove broken link
Co-authored-by: Alfred Gedeon <gedeonag@amazon.com>
bbain
Dusan Cervenka
Paul Bartell
Cristian Cristea
Gaurav-Aggarwal-AWS
Gavin Lambert
j4cbo
Cobus van Eeden
David Chalco
David Chalco
RichardBarry
alfred gedeon
Alfred Gedeon
Yuhui.Zheng