//
// This must be called from the system stack and the user goroutine on
// the current M (if any) must be in a preemptible state. This
// prevents deadlocks where two goroutines attempt to suspend each
// other and both are in non-preemptible states. There are other ways
// to resolve this deadlock, but this seems simplest.
//
// TODO(austin): What if we instead required this to be called from a

	// Drain the pool of idle time.
	idleTime := l.idleTimePool.Load()
	if idleTime != 0 {
		l.idleTimePool.Add(-idleTime)
	}

	if !l.test {
		// Consume time from in-flight events. Make sure we're not preemptible so allp can't change.
		//
		// The reason we do this instead of just waiting for those events to finish and push updates
		// is to ensure that all the time we're accounting for happened sometime between lastUpdate

}

// setUserArenaChunkToFault sets the address space for the user arena chunk to fault
// and releases any underlying memory resources.
//
// Must be in a non-preemptible state to ensure the consistency of statistics
// exported to MemStats.
func (s *mspan) setUserArenaChunkToFault() {
	if !s.isUserArenaChunk {
		throw("invalid span in heapArena for user arena")
	}

func gcStart(trigger gcTrigger) {
	// Since this is called from malloc and malloc is called in
	// the guts of a number of libraries that might be holding
	// locks, don't attempt to start GC in non-preemptible or
	// potentially unstable situations.
	mp := acquirem()
	if gp := getg(); gp == mp.g0 || mp.locks > 1 || mp.preemptoff != "" {
		releasem(mp)
		return
	}
	releasem(mp)
	mp = nil

#  DELETE_INSTANCES: For REMOTE=true only.  Delete any instances created as
#    part of this test run.  Defaults to false.
#  PREEMPTIBLE_INSTANCES: For REMOTE=true only.  Mark created gce instances
#    as preemptible.  Defaults to false.
#  CLEANUP: For REMOTE=true only.  If false, do not stop processes or delete
#    test files on remote hosts.  Defaults to true.
#  IMAGE_PROJECT: For REMOTE=true only.  Project containing images provided to

					// during the execution of the function prologue, the traceback
					// code will not see a half-updated stack frame.
					// This sequence is not async preemptible, as if we open a frame
					// at the current SP, it will clobber the saved LR.
					q = obj.Appendp(q, c.newprog)
					q.As = AMOVD
					q.Pos = p.Pos
					q.From.Type = obj.TYPE_REG
					q.From.Reg = REG_LR

// weight allocation. If it is a heavy weight allocation the caller must
// determine whether a new GC cycle needs to be started or if the GC is active
// whether this goroutine needs to assist the GC.
//
// Must run in a non-preemptible context since otherwise the owner of
// c could change.
func (c *mcache) nextFree(spc spanClass) (v gclinkptr, s *mspan, shouldhelpgc bool) {
	s = c.alloc[spc]
	shouldhelpgc = false
	freeIndex := s.nextFreeIndex()

	// hits a traceAcquire, it sees that the trace is enabled.
	//
	// Note also that stopping the world is necessary to make sure sweep-related events are
	// coherent. Since the world is stopped and sweeps are non-preemptible, we can never start
	// the world and see an unpaired sweep 'end' event. Other parts of the tracer rely on this.
	stw := stopTheWorld(stwStartTrace)

	// Prevent sysmon from running any code that could generate events.

			n := stack[tos]
			if n.l == nil {
				tos--
			} else {
				n.l, n.r = n.r, n.l
				stack[tos] = n.l
				stack[tos+1] = n.r
				tos++
			}

			if i%(1<<12) == 0 {
				// Avoid non-preemptible loops (see issue #10958).
				runtime.Gosched()
			}
		}
	})

	runtime.KeepAlive(wbRoots)
}

func BenchmarkBulkWriteBarrier(b *testing.B) {
	if runtime.GOMAXPROCS(-1) < 2 {

	execution tracer to double-check stack ownership before taking a stack trace.

	asyncpreemptoff: asyncpreemptoff=1 disables signal-based
	asynchronous goroutine preemption. This makes some loops
	non-preemptible for long periods, which may delay GC and
	goroutine scheduling. This is useful for debugging GC issues
	because it also disables the conservative stack scanning used
	for asynchronously preempted goroutines.