Kuidas võib tekkida olukord, kus madalama prioriteediga järjekord saab juurdepääsu ressurssidele enne kõrgema prioriteediga järjekorda?

This can happen due to priority inversion.

Priority inversion occurs when a low-priority task holds a resource (e.g., a mutex) needed by a high-priority task. The high-priority task gets blocked, waiting for the resource to be released. Meanwhile, a medium-priority task, which does not need the resource, can preempt the low-priority task. As a result, the medium-priority task executes while the low-priority task, holding the resource, and the high-priority task, blocked, are waiting. The high-priority task effectively waits until the medium-priority task completes and the low-priority task releases the resource.

Solutions to priority inversion:

• Priority Inheritance: When a low-priority task holds a resource needed by a high-priority task, it temporarily inherits the high-priority task's priority. After releasing the resource, its priority reverts to the original.
• Priority Ceiling Protocol: Each resource is assigned a "priority ceiling" — the highest priority among all tasks that may use this resource. A task can access the resource only if its current priority is higher than the ceiling of all currently occupied resources (including those it already holds).

In iOS, Grand Central Dispatch (GCD) and Operation Queues have mechanisms to minimize priority inversion, but such situations can still occur in complex locking scenarios if used improperly.