How are system calls that block the execution of processes or threads implemented?

System calls that block the execution of processes or threads work as follows: when a process or thread invokes such a system call (for example, reading from a file or waiting for an event), execution is suspended until the operation completes. During this time, the OS kernel switches the process or thread to a waiting state (blocked), freeing the CPU for other tasks.

In Go, when calling blocking system calls, the runtime uses goroutine and system thread scheduler mechanisms. If a goroutine blocks on a system call, the runtime can switch execution to another goroutine without blocking the entire OS thread. This achieves efficient resource utilization and parallelism.

Example: when reading from a network using net.Conn.Read(), the goroutine blocks, but the runtime switches to other goroutines until the data is received.