ret := int(gomaxprocs)
	unlock(&sched.lock)
	if n <= 0 || n == ret {
		return ret
	}

	stw := stopTheWorldGC(stwGOMAXPROCS)

	// newprocs will be processed by startTheWorld
	newprocs = int32(n)

	startTheWorldGC(stw)
	return ret
}

// NumCPU returns the number of logical CPUs usable by the current process.
//
// The set of available CPUs is checked by querying the operating system

				{"time.Sleep", 0},
				{"main.main", 0},
			}},
			{trace.EventMetric, "/sched/gomaxprocs:threads", []frame{
				{"runtime.startTheWorld", 0}, // this is when the current gomaxprocs is logged.
				{"runtime.startTheWorldGC", 0},
				{"runtime.GOMAXPROCS", 0},
				{"main.main", 0},
			}},
		}
		if !stress {
			// Only check for this stack if !stress because traceAdvance alone could

// until the GC is not running. It also blocks a GC from starting
// until startTheWorldGC is called.
func stopTheWorldGC(reason stwReason) worldStop {
	semacquire(&gcsema)
	return stopTheWorld(reason)
}

// startTheWorldGC undoes the effects of stopTheWorldGC.
//
// w must be the worldStop returned by stopTheWorld.
func startTheWorldGC(w worldStop) {
	startTheWorld(w)
	semrelease(&gcsema)
}