2 docs tagged with "semaphore"

Threads within a process share memory, which makes communication cheap but introduces a real hazard:

Adding a scheduler adds a second way for code to be interrupted. On bare metal the only thing that could run between your load and your store was an exception handler, and Critical Sections and Atomicity is the complete answer to that. Under a kernel, a task can also be pre-empted by another task, at any instruction, for reasons that have nothing to do with the NVIC. Masking interrupts no longer covers the hazard, because the thing that pre-empted you was the scheduler doing its job.