CircularBuffer: volatile specifier removal

[0xc0170]

Volatile specifier in this case it not required as we currently have all accesses
to the buffer protected by critical section. This shall optimize accesses in
some cases to the buffer.

Fixes #7702

Description

Pull request type

[ ] Fix
[X] Refactor
[ ] Target update
[ ] Feature
[ ] Breaking change

[kjbracey]

Only thing to worry about I can see is construction, but any execution context that invokes the constructor and then hands the buffer to another context /should/ already have its own ordering for that handover, otherwise the handover would be a race.

But this is not a "fix". It's not fixing an actual bug, and it could conceivably trip a problem in something lacking correct init synchronisation.

[0xc0170]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 2759
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7727/

Triggering tests

/morph test
/morph uvisor-test
/morph export-build
/morph mbed2-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2388
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7727/

[mbed-ci]

Test : FAILURE

Build number : 2485
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7727/2485

[cmonr]

Hmm...
/morph test

But this is not a "fix". It's not fixing an actual bug, and it could conceivably trip a problem in something lacking correct init synchronisation.

@kjbracey-arm Like for example, the lp-timeout callback test?

[mbed-ci]

Test : SUCCESS

Build number : 2494
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7727/2494

[bmcdonnell-ionx]

@cmonr / @0xc0170,

Do you think it's likely that someone else will look at the code in the future and ask questions rehashing the conversation in #7702? If so, consider adding comments in the code.

[kjbracey]

Once the volatiles have gone from here, not sure it's worth noting their absence.

I think it is worth noting in the documentation of the enter/exit critical functions themselves. If you're using those functions, using ordinary variables without volatile should be as "routine" as using variables without volatile in multiple threads with Mutex::lock().

[kjbracey]

Relabelled as a refactor and release in 5.10.

[0xc0170]

Do you think it's likely that someone else will look at the code in the future and ask questions rehashing the conversation in #7702? If so, consider adding comments in the code.

@bmcdonnell-ionx The details are in the commit message (why they are being removed and what we are fixing). I found it sufficient for this case.

[mbed-ci]

Exporter Build : FAILURE

Build number : 2407
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7727/