armcc fopen allocated a mutex using the retargeted system-level
_mutex_initialize function. Interestingly, malloc also uses this
same _mutex_initialization function, which prevents a full solution
relying on malloc. The solution previously implemented involved using
the rtx mutex pool for the first 8 mutexes, then falling back on
malloc.
The previous implementation relied on osMutexNew returning an error
on out-of-memory. An unrelated change causes osMutexNew to instead
assert (except for release mode). This meant if you exceed 8 system-
level mutexes in armcc you will hit an assert. Since the filesystem
code can call fopen an unlimited number of times, this is a problem.
Solution is to keep track of which static mutexes we've allocated, so
we know before calling osMutexNew if we need to call malloc.
Also _mutex_free never deallocated the malloced mutexes, which would
cause fopen to leak memory.
Update directory structure to include RTX for only cortex targets, and
for all cortex targets. This patch accomplishes this by moving mbed-os
specific RTX files and RTX itself into rtos/TARGET_CORTEX along with
removing TARGET_CORTEX_M from the RTX5 directory.
The old directory structure:
rtos/rtx5/<mbed-os specific RTX files>
rtos/rtx5/TARGET_CORTEX_M/*
rtos/rtx4/*
rtos/<mbed-os specific RTX files>
Is re-arranged to:
rtos/TARGET_CORTEX/rtx5/*
rtos/TARGET_CORTEX/rtx4/*
rtos/TARGET_CORTEX/<mbed-os specific rtx files>
This both encapsulates RTX code more cleanly and makes it easier to
experiment with non-cortex cmsis-os2 backends, such as a posix
based cmsis-os2 backend.
Note - A potentially better name for the CORTEX_M directory would be
something like FEATURE_RTX5 since this directory only contains RTX5
related files. This cannot be done because there is not an easy way
to turn this feature on, since it cannot be done from mbed_lib.json.
Senthil Ramakrishnan
Christopher Haster
Jimmy Brisson
Deepika
Russ Butler