Support for synchronization primitives located in stk::sync namespac

[dmitrykos]

Currently supported:

• ScopedCriticalSection
• ConditionVariable
• Event
• Mutex
• Semaphore
• Pipe

All these primitives can be used as a building blocks for other synchronization implementation (see Pipe which is using ConditionVariable).

There is an example demonstrating synchronization primitives for x86, ARM and RISC-V archs in action:

• in build/example/sync folder
• corresponding Eclipse projects in x86, stm, rpi directories

There are additional tests (work in progress in this PR).

To support synchronization primitives Kernel must be configured with a new KERNEL_SYNC flag. Obviously, if KERNEL_SYNC is not set then all synchronization-related support is removed by the compiler (no binary bloat due to this new feature).

This PR is work in progress and will be merged when work on test coverage and C interface is completed. New C++ API is stable, so you can use implementation already in your C++ project.

Demo:

#include <stk.h>
#include <sync/stk_sync.h>

enum LedState { LED_OFF, LED_ON };

// One-slot pipe for passing LED states between tasks
static stk::sync::Pipe<LedState, 1> g_CtrlSignalPipe;
static stk::sync::Mutex g_HwMutex;

// Consumer Task: Waits for state updates from the pipe
template <stk::EAccessMode _Mode>
class LedTask : public stk::Task<2048, _Mode> {
    void RunInner() {
        LedState target_state;
        while (true) {
            // Blocks until a signal is received or 100ms timeout occurs
            if (g_CtrlSignalPipe.Read(target_state, 100)) {
                stk::sync::Mutex::ScopedLock guard(g_HwMutex);
                Led::Set(Led::GREEN, (target_state == LED_ON));
            }
        }
    }
};

// Producer Task: Writes new states to the pipe
template <stk::EAccessMode _Mode>
class CtrlTask : public stk::Task<256, _Mode> {
    void RunInner() {
        bool led_sw = false;
        while (true) {
            stk::Sleep(250);
            led_sw = !led_sw;
            // Write new state to the pipe for the LedTask to consume
            g_CtrlSignalPipe.Write(led_sw ? LED_ON : LED_OFF);
        }
    }
};

[github-actions]

MemBrowse Memory Report

stm32f0-sleep

• RAM: .bss +16 B (+0.3%, 6,300 B / 8,192 B, total: 77% used)
• FLASH: .text +308 B (+1.7%, 18,156 B / 65,536 B, total: 28% used)

stm32f1-sleep

• RAM: .bss +16 B (+0.3%, 6,300 B / 20,480 B, total: 31% used)
• FLASH: .text +368 B (+2.2%, 17,469 B / 131,072 B, total: 13% used)

stm32f4-sleep

• RAM: .bss +16 B (+0.3%, 6,304 B / 131,072 B, total: 5% used)
• FLASH: .text +368 B (+2.0%, 18,353 B / 1,048,576 B, total: 2% used)

[github-actions]

LCOV of commit f2e3f78 during Code Coverage - Generic #300

Summary coverage rate:
  lines......: 100.0% (936 of 936 lines)
  functions..: 55.2% (1190 of 2156 functions)
  branches...: no data found

Files changed coverage rate: n/a

[github-actions]

LCOV of commit db9054c during Code Coverage - Generic #301

Summary coverage rate:
  lines......: 100.0% (936 of 936 lines)
  functions..: 55.2% (1190 of 2156 functions)
  branches...: no data found

Files changed coverage rate: n/a