Inconsistent thread safety implementation

[neilt6]

Most of the new thread safe classes are using a single static mutex for all instances. This guarantees thread safety across multiple objects, but prevents multiple independent peripherals from being used simultaneously. Kind of inconvenient, but developers can override the virtual lock() and unlock() methods to disable the mutex so not a big deal.

However, AnalogOut, CAN, SPI, and Serial are using separate mutexes for each instance. This guarantees nothing unless the developer creates a single object and passes it around, which is not the way these objects have historically been used. Is this implementation a mistake, or by design?

[0xc0170]

cc @c1728p9

[c1728p9]

Hi @neilt6, this behavior was intentional for AnalogOut, CAN, and Serial since the typical use case it to only have one instance of these objects per hardware resource. SPI, similar to IIC, can have multiple instances bound to the same hardware, so this should be using a shared mutex.

[neilt6]

@c1728p9 - Thanks for the clarification. My main concern was SPI, I'm less familiar with the others. Would you like me to submit a pull-request modifying SPI to use a SingletonPtr?

[c1728p9]

@neilt6, yeah a PR would be great! Thanks