// Ensure the map is initialized.
	initMetrics()

	// Read the metrics.
	readMetricsLocked(samplesp, len, cap)
	metricsUnlock()
}

// readMetricsLocked is the internal, locked portion of readMetrics.
//
// Broken out for more robust testing. metricsLock must be held and
// initMetrics must have been called already.
func readMetricsLocked(samplesp unsafe.Pointer, len int, cap int) {
	// Construct a slice from the args.

	metricsLock()
	initMetrics()

	systemstack(func() {
		// Donate the racectx to g0. readMetricsLocked calls into the race detector
		// via map access.
		getg().racectx = getg().m.curg.racectx

		// Read the metrics once before in case it allocates and skews the metrics.
		// readMetricsLocked is designed to only allocate the first time it is called