Recursive mutex / newlib retarget lock support

[Wiz-IO]

Please add support for recursive mutex
mutex_enter_blocking_recursive()
mutex_try_enter_recursive()
mutex_exit_recursive()

[lurch]

ping @kilograham

[Wiz-IO]

just for info ... look this
https://github.com/Wiz-IO/LIB/blob/master/pico/pico_mutex/mutex.c#L82
new is only one counter in mutex_t
https://github.com/Wiz-IO/LIB/blob/master/pico/pico_mutex/mutex.h#L35

results with <sys/lock.h>
no locks
with locks

[kilograham]

results with <sys/lock.h>
no locks
with locks

Not 100% sure what you are trying to indicate here... I know what a mutex does :-) ... FYI printf in the SDK is already mutex-ed for you by default.

[Wiz-IO]

recursive mutex is used for "future" ..... <sys/lock.h> as baremetal and/or FreeRTOS to protect the stdio and file system

[Wiz-IO]

example: unistd and FILE in Arduino (C++)
RAM Disk + FLASH Disk + SD Card
posix? :) ... need only 5 functions for pthread...

[kilograham]

So the existing mutex classes should not be used in a FreeRTOS as they are core not task focused (unless you specifically mean core).

Equally, should a recursive mutex be successfully claimed by both application and IRQ on the same core?

[Wiz-IO]

https://github.com/Wiz-IO/framework-wizio-pico/blob/main/wizio/newlib/lock.c

[kilograham]

showing me that code doesn't really answer my question, though I am able to glean that you seem to want the recursive mutexes to work the way that makes them suitable for using in newlib locking (which isn't documented there). (edit i mean you showed me locks that are re-entrant on the same core, I still don't know if this is desirable behavior though for an IRQ to be able to take a lock owned by the application code).

Can you point me at some docs for the newlib locking - since you seem to be implementing the locks defined somewhere, because fixing enabling newlib re-entrancy/locking when using multicore via the raw SDK is likely a good thing anyway (note I was assuming the newlib that comes with gcc just didn't support it, but I guess I am wrong).

[Wiz-IO]

I was looking for documents for newlib
found only this...
https://www.cs.ccu.edu.tw/~pahsiung/courses/ese/resources/newlib.pdf

and I applied this in reverse
https://gist.github.com/thomask77/65591d78070ace68885d3fd05cdebe3a

here is my version (as idea)
is only one counter in mutex_t and this
https://github.com/Wiz-IO/framework-wizio-pico/blob/main/SDK/pico/pico_sync/mutex.c#L82

[kilograham]

Note recursive mutexes will be added by #378

[lurch]

...have been added... 🙂 (i.e. this can be closed?)

[Wiz-IO]

yep close
this days will test...