fix(IoT): fixing race condition in AWSIoTStreamThread .cxx_destruct …

[AndrKonovalov]

Issue #, if available:
#5452

Description of changes:

1. Addition of Synchronization Primitives New Properties:

• dispatch_queue_t cleanupQueue
• dispatch_semaphore_t cleanupSemaphore
• BOOL isCleaningUp Purpose: Ensures thread-safe access and modification of critical properties like isRunning, shouldDisconnect, and defaultRunLoopTimer. Synchronization prevents race conditions during cleanup and cancellation processes.

2. Enhanced shouldContinueRunning Method

• Before: Used direct property access without synchronization
• After: Introduced synchronization using dispatch_sync for thread-safe checks
• Purpose:Prevents inconsistencies if multiple threads attempt to read/write properties simultaneously.

3. Cleanup Enhancements

• performCleanup and cleanupResources:
• Added explicit synchronization: dispatch_sync and dispatch_semaphore ensure cleanup operations are thread-safe and do not overlap if called multiple times. Handles complex cleanup sequences safely, such as invalidating timers, disconnecting streams, and deallocating the session.
• Purpose: Ensures that cleanup actions (e.g., closing streams and invalidating timers) are thread-safe and only executed once.

4. Timer Initialization Weak Reference to Prevent Retain Cycles.

• The timer in setupRunLoop now uses a __weak reference to avoid retain cycles
• Before: Used a strong reference (target:self), which could result in a retain cycle.
• Purpose: Avoids potential memory leaks by ensuring the thread does not retain itself via the timer.

6. Improved cancel Method

• Before: Simple isRunning flag and direct super cancel call

• After: Introduced thread-safe handling and ensured timer invalidation

• Purpose: Prevents race conditions when canceling the thread, ensuring timers are invalidated and properties are safely updated.
  Check points:

• [ x] Added new tests to cover change, if needed

• All unit tests pass

• All integration tests pass

• Updated CHANGELOG.md

• Documentation update for the change if required

• PR title conforms to conventional commit style

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[harsh62]

Failing unit tests:

Failing tests:
	-[AWSIoTStreamThreadTests testCancel_shouldNotCloseStreams_andInvokeOnStop]
	-[AWSIoTStreamThreadTests testCancelAndDisconnect_shouldCloseStreams_andInvokeOnStop]
	-[AWSIoTStreamThreadTests testCancelAndDisconnect_shouldSetIsCleaningUp]
	-[AWSIoTStreamThreadTests testCancelAndDisconnect_shouldSynchronizeOnCleanupQueue]
	-[AWSIoTStreamThreadTests testInvalidateTimer_shouldInvalidateAndSetTimerToNil]
	-[AWSIoTStreamThreadTests testRunLoop_shouldInvokeRunModeBeforeDate]
	-[AWSIoTStreamThreadTests testStart_shouldOpenStream_andInvokeConnectOnSession]

[harsh62]

Tests need to be fixed.

[ruisebas]

Closing in favour of #5477