On 28/07/2021 21:54, Gedare Bloom wrote:
Hello all,
In most (all?) the SMP ports, we have in the CPU Context Control:
bool is_executing;
Yes, all SMP ports need this. It is used to implement a TTAS lock in the
context switch:
https://docs.rtems.org/branches/master/c-user/symmetric_multiprocessing_services.html#thread-dispatch-details
This variable often is accessed through assembly language (i.e.,
during the context switch), using something like
ARCH_CONTEXT_CONTROL_IS_EXECUTING_OFFSET. Unfortunately, the 'bool'
type is not standard, or rather its size is implementation-defined. I
think it is generally an 8-bit value though for us. I see that the
riscv port uses explicitly a uint32_t so that's nice.
I think we should replace 'bool' with uint8_t in the other ports that
are using byte-size accesses from assembly, just to be well-defined.
Most likely, this doesn't actually affect anything and I'm just a
little paranoid.
Is the bool size and alignment not defined by the ABI? We don't have to
use this type, we could also use an uint32_t or whatever. The convention
is that a zero value is false, everything else is true.
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