Fix lock api

[fjtrujy]

To have thread-safe operations for all the newlib operations we have been required to do several PR:

• newlib
• psptoolchain-ee
• pspsdk

This PR skips the usage of the dummy lock API, letting us implement the specific one in the pspsdk/libcglue

Cheers

[fjtrujy]

fix dummy warning

[fjtrujy]

Adding extra documentation for lightweight mutex

[diamant3]

Thank you for the PRs @fjtrujy

[rofl0r]

it's kinda odd that the PSP kernel even ships these functions since it's inherently non-parallel with its use of cooperative multitasking, except when using the Media Engine CPU - but from what i gathered from looking at the code of uofw, for those locks it uses custom code. maybe @fjtrujy can shed some light ?

[fjtrujy]

it's kinda odd that the PSP kernel even ships these functions since it's inherently non-parallel with its use of cooperative multitasking, except when using the Media Engine CPU - but from what i gathered from looking at the code of uofw, for those locks it uses custom code. maybe @fjtrujy can shed some light ?

Not sure what specific stuff do you want to know more about?
Do you mean about recursive mutex?

[rofl0r]

no, i mean why does the PSP OS provide mutexes, locks and semaphores when there's no real parallel execution ?

[fjtrujy]

no, i mean why does the PSP OS provide mutexes, locks, and semaphores when there's no real parallel execution?

If you have a fully single thread, obviously you can’t have concurrency issues, but as soon as you start “emulating threads” (have in mind that PSP hardware is still a single thread), you must have them otherwise you can suffer concurrency issues.
The swap between threads in PSP happens as soon as the current thread enters sleep mode (tons of ways to do this, the easiest is to run nanosleep function), or because interruptions with higher priorities are executed, jumping to a different part of your code… this is why, sometimes you see how interruptions are disabled, in this way, you can assure your execution is not going to stop and jump to a different place… (that was the very first implementation of thread safe allocation on newlib in PSP years ago…)
Not sure if I have replied to your question, but this is a generic question in terms of “concurrency issues“