> Makes you think, do Linux, Windows and Mac handle this properly? Honestly, I doubt it! Rubbish. These kernels (well Linux and Windows) run on systems with hu

> Makes you think, do Linux, Windows and Mac handle this properly? Honestly, I doubt it! Rubbish. These kernels (well Linux and Windows) run on systems with hundreds even thousands of cores, on CPUs which are very weakly ordered, with a pretty reasonable level of reliability. A race like this will blow up immediately. Linux handles this by requiring that a context switch operation includes a full memory barrier so switching off CPU0 has a barrier ordering prior stores on CPU0 with storing a field that implies the task can be migrated (it's not currently running), and switching on to CPU1 has a barrier ordering the load of that flag with subsequent loads from the task on CPU1. EDIT: here - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/sched/core.c#n3933 https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin... * The basic program-order guarantee on SMP systems is that when a task [t] * migrates, all its activity on its old CPU [c0] happens-before any subsequent * execution on its new CPU [c1]. It's informally worded but "activity" basically means memory operations (but could include whacky arch and platform specific things to cover all bases), and "happens before" meaning observable from other CPUs, which is clear in context.