This commit updates the FreeRTOS port FPU unit tests so that they run for
multiple iterations, thus checking that a task's FPU context is properly
cleaned up on deletion.
Previously, IDF FreeRTOS would restrict the clean up of task memory (done by
vTaskDelete() or the Idle task) to only tasks pinned to the current core or
unpinned tasks. This was due to the need to clear the task's coprocessor
ownership on the other core (i.e., "_xt_coproc_owner_sa"). But this restriction
can be lifted by simply protecting access of "_xt_coproc_owner_sa" with a
spinlock.
This commit implements a "_xt_coproc_owner_sa_lock" to protect the access of
"_xt_coproc_owner_sa", thus vTaskDelete() and prvDeleteTCB() can now delete
tasks pinned to the other core so long as that task is not currently running.
Note: This fix was copied from the Xtensa port of Amazon SMP FreeRTOS
This commit removes the dependency on portUSING_MPU_WRAPPERS on the Xtensa port
of IDF FreeRTOS. This dependency was added due to a hack implemented in the
upstream port that required the usage of the "xMPUSettings" member of the TCB.
The "xMPUSettings" would be used as a pointer to the task's coprocessor save
area on the stack, even though FreeRTOS MPU support was not available.
The hack has now been removed, and the CPSA pointer is now calculated using
a combination of constant offsets values and the pxEndOfStack member of the
TCB.
Note: This impelemtation was copied from the Xtensa port of Amazon SMP FreeRTOS.
This commit refactors the FPU handling code on the Xtensa port of Amazon SMP
FreeRTOS in the following ways:
Auto-pinning via XT_RTOS_CP_EXC_HOOK
------------------------------------
The "_xt_coproc_exc" exception would previously automatically pin a task that
uses the FPU to the current core (to ensure that we can lazy save the task's FPU
context). However, this would mean that "xtensa_vectors.S" would need to be
OS-aware (to read the task's TCB structure).
This is now refactored so that "_xt_coproc_exc" calls a CP exception hook
function ("XT_RTOS_CP_EXC_HOOK") implemented in "portasm.S", thus allowing
"xtensa_vectors.S" to remain OS agnostic.
Using macros to acquire owner spinlock
--------------------------------------
The taking and relasing of the "_xt_coproc_owner_sa_lock" is now mostly
abstracted as the "spinlock_take" and "spinlock_release" macro. As a result,
"_xt_coproc_release" and "_xt_coproc_exc" are refactored so that:
- They are closer to their upstream (original) versions
- The spinlock is only taken when building for multicore
- The spinlock held region is shortened (now only protects the instructions
that access the "_xt_coproc_owner_sa" array
Other Changes
-------------
- Updated placing and comments of various "offset_..." constants used by
portasm.S
- Update description of "get_cpsa_from_tcb" assembly macro
- Tidied up some typos in the ".S" files
This commit fixes the following FPU/Coprocessor bugs in the Xtensa port of
Amazon SMP FreeRTOS:
- vPortCleanUpCoprocArea() does not calculate the correct pointer to the
task's CPSA (located on the task's stack). This can result in
- _xt_coproc_release() not releasing the task's CP ownership
- The next coprocessor exception will write the current CP owner (i.e., the
deleted task's CPSA) leading to memory corruption
- _xt_coproc_release() writes xCoreID instead of 0 when clearing a CP owner.
This results in the next CP exception trying to load the CP owner's CPSA at
the address of "xCoreID", leading to a double exception.
