4 docs tagged with "mutex"

Boost.Thread provides portable threading primitives — threads, mutexes, condition variables, futures,

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

A priority is a promise about who gets the core when two tasks want it. A lock is a mechanism that can break that promise, and the reason is structural rather than accidental: a task holding a lock has implicitly borrowed the urgency of every task that will ever wait for it, and the scheduler has no way of knowing that until someone actually waits. Until that moment the holder is running at its own priority, and the system is scheduling a task that is, in effect, on the critical path of something far more urgent.

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.