// operations like close().
	return unsafe.Pointer(&c.buf)
}

func racesync(c *hchan, sg *sudog) {
	racerelease(chanbuf(c, 0))
	raceacquireg(sg.g, chanbuf(c, 0))
	racereleaseg(sg.g, chanbuf(c, 0))
	raceacquire(chanbuf(c, 0))
}

// Notify the race detector of a send or receive involving buffer entry idx
// and a channel c or its communicating partner sg.

// In terms of the C memory model (C11 §5.1.2.4, §7.17.3),
// RaceAcquire is equivalent to atomic_load(memory_order_acquire).
//
//go:nosplit
func RaceAcquire(addr unsafe.Pointer) {
	raceacquire(addr)
}

// RaceRelease performs a release operation on addr that
// can synchronize with a later RaceAcquire on addr.
//
// In terms of the C memory model, RaceRelease is equivalent to

			tl := traceAcquire()
			if !pp.trace.statusWasTraced(tl.gen) {
				tl.writer().writeProcStatusForP(pp, false).end()
			}
			traceRelease(tl)
		})
		semrelease(&worldsema)
	}

	// Block until the trace reader has finished processing the last generation.
	semacquire(&trace.doneSema[gen%2])
	if raceenabled {
		raceacquire(unsafe.Pointer(&trace.doneSema[gen%2]))
	}

// not inlineable, and we want traceAcquire to be inlineable for
// low overhead when the trace is disabled.
const debugTraceReentrancy = false

// traceAcquire prepares this M for writing one or more trace events.
//
// nosplit because it's called on the syscall path when stack movement is forbidden.
//
//go:nosplit
func traceAcquire() traceLocker {
	if !traceEnabled() {
		return traceLocker{}

			// Like the runtime/pprof package, even if that bug didn't exist
			// we would still want to do a goroutine-level sleep in between
			// reads to avoid frequent wakeups.
			trace.cpuSleep.sleep(100_000_000)

			tl := traceAcquire()
			if !tl.ok() {
				// Tracing disabled.
				break
			}
			keepGoing := traceReadCPU(tl.gen)
			traceRelease(tl)
			if !keepGoing {
				break
			}
		}
		done <- struct{}{}
	}()

	// used again if callback decide to make syscall.
	winsyscall := mp.winsyscall

	exitsyscall()

	getg().m.winsyscall = winsyscall

	// Note that raceacquire must be called only after exitsyscall has
	// wired this M to a P.
	if raceenabled {
		raceacquire(unsafe.Pointer(&racecgosync))
	}

	// From the garbage collector's perspective, time can move
	// backwards in the sequence above. If there's a callback into

		// might call into the tracer, and the tracer is non-reentrant.
		trace := traceAcquire()
		if s == _Psyscall && p2.runSafePointFn == 1 && atomic.Cas(&p2.status, s, _Pidle) {
			if trace.ok() {
				// It's important that we traceRelease before we call handoffp, which may also traceAcquire.
				trace.ProcSteal(p2, false)
				traceRelease(trace)
			}
			p2.syscalltick++
			handoffp(p2)

	w.varint(uint64(pageSize))
	w.varint(uint64(minHeapAlign))
	w.varint(uint64(fixedStack))

	// Finish writing the batch.
	w.flush().end()

	// Start tracing.
	trace := traceAcquire()
	if !trace.ok() {
		throw("traceSnapshotMemory: tracing is not enabled")
	}

	// Write out all the heap spans and heap objects.
	for _, s := range mheap_.allspans {
		if s.state.get() == mSpanDead {

}

func cbsLock() {
	lock(&cbs.lock)
	// compileCallback is used by goenvs prior to completion of schedinit.
	// raceacquire involves a racecallback to get the proc, which is not
	// safe prior to scheduler initialization. Thus avoid instrumentation
	// until then.
	if raceenabled && mainStarted {
		raceacquire(unsafe.Pointer(&cbs.lock))
	}
}

func cbsUnlock() {
	if raceenabled && mainStarted {

		print("mspan.sweep: state=", state, " sweepgen=", s.sweepgen, " mheap.sweepgen=", sweepgen, "\n")
		throw("mspan.sweep: bad span state")
	}

	trace := traceAcquire()
	if trace.ok() {
		trace.GCSweepSpan(s.npages * _PageSize)
		traceRelease(trace)
	}

	mheap_.pagesSwept.Add(int64(s.npages))

	spc := s.spanclass
	size := s.elemsize