The atomic functions preserve volatile semantics - they only perform the
accesses specified. Add the volatile qualifier to the value pointer to
reflect this. This does not change existing caller code - it's
equivalent to adding a const qualifier to indicate we don't write to
a pointer - it means people can pass us qualified pointers without
casts, letting the compile check const- or volatile-correctness.
This is consistent with C11 <stdatomic.h>, which volatile-qualifies its
equivalent functions.
Note that this useage of volatile has nothing to do with the atomicity -
objects accessed via the atomic functions do not need to be volatile.
But it does permit these calls to be used on objects which have been
declared volatile.
- Define header functions for Critical Section HAL API
- hal_critical_section_enter()
- hal_critical_section_exit()
- Add weak default implementation for HAL API. The default implementation
matches the previous behaviour stored in mbed_critical:
- The first call to enter a critical section stores the state of interrupts
before disabling and each successive call re-disables interrupts.
- The last call (non-nested) will restore the IRQ state that was set on the
enter to the critical section. Nested calls are ignored.
- Add function 'core_util_in_critical_section' to User facing API to determine
if the program is currently in a critical section, instead of depending on
'core_util_interrupts_enabled'.
Add a note to each CAS making explicit that the functions are strong.
Minor wording change to expectedCurrentValue - use of "still updated"
about the failure case suggested that it might be written to on success.
For some uses it's critically important that expectedCurrentValue only
be written on failure, so change wording to "instead updated".
Kevin Bracey
Steven Cartmell
Senthil Ramakrishnan
Russ Butler
Sam Grove
Christopher Haster