package sync

import "unsafe"

// defined in package runtime

// Semacquire waits until *s > 0 and then atomically decrements it.
// It is intended as a simple sleep primitive for use by the synchronization
// library and should not be used directly.
func runtime_Semacquire(s *uint32)

// Semacquire(RW)Mutex(R) is like Semacquire, but for profiling contended
// Mutexes and RWMutexes.

				default:
				}
				Gosched()
			}
		}()
	}

	wg.Add(1)
	go func() {
		defer wg.Done()
		Semacquire(&sema)
		atomic.CompareAndSwapUint32(&res, 0, 1)

		Semrelease1(&sema, true, 0)
		close(done)
	}()
	for SemNwait(&sema) == 0 {
		Gosched() // wait for goroutine to block in Semacquire
	}

	// The crux of the test: we release the semaphore with handoff

	semaMutexProfile
)

// Called from runtime.
func semacquire(addr *uint32) {
	semacquire1(addr, false, 0, 0, waitReasonSemacquire)
}

func semacquire1(addr *uint32, lifo bool, profile semaProfileFlags, skipframes int, reason waitReason) {
	gp := getg()
	if gp != gp.m.curg {
		throw("semacquire not on the G stack")
	}

	// Easy case.
	if cansemacquire(addr) {
		return
	}

		return errorString("tracing is already enabled")
	}
	// Block until cleanup of the last trace is done.
	semacquire(&traceShutdownSema)
	semrelease(&traceShutdownSema)

	// Hold traceAdvanceSema across trace start, since we'll want it on
	// the other side of tracing being enabled globally.
	semacquire(&traceAdvanceSema)

	// Initialize CPU profile -> trace ingestion.
	traceInitReadCPU()

	if debug.gcstoptheworld == 1 {
		mode = gcForceMode
	} else if debug.gcstoptheworld == 2 {
		mode = gcForceBlockMode
	}

	// Ok, we're doing it! Stop everybody else
	semacquire(&gcsema)
	semacquire(&worldsema)

	// For stats, check if this GC was forced by the user.
	// Update it under gcsema to avoid gctrace getting wrong values.
	work.userForced = trigger.kind == gcTriggerCycle

	waitReasonFinalizerWait                           // "finalizer wait"
	waitReasonForceGCIdle                             // "force gc (idle)"
	waitReasonSemacquire                              // "semacquire"
	waitReasonSleep                                   // "sleep"
	waitReasonSyncCondWait                            // "sync.Cond.Wait"
	waitReasonSyncMutexLock                           // "sync.Mutex.Lock"

				"runtime.semrelease1",
				"runtime_test.TestRuntimeLockMetricsAndProfile.func6.1",
				"runtime_test.(*contentionWorker).run",
			},
			{
				"runtime.unlock",
				"runtime.semacquire1",
				"runtime.semacquire",
				"runtime_test.TestRuntimeLockMetricsAndProfile.func6.1",
				"runtime_test.(*contentionWorker).run",
			},
		}

var Lock = lock
var Unlock = unlock

var MutexContended = mutexContended

func SemRootLock(addr *uint32) *mutex {
	root := semtable.rootFor(addr)
	return &root.lock
}

var Semacquire = semacquire
var Semrelease1 = semrelease1

func SemNwait(addr *uint32) uint32 {
	root := semtable.rootFor(addr)
	return root.nwait.Load()
}

const SemTableSize = semTabSize

		// allocation estimate without bothering to STW. As long as
		// this is close, then we'll only need to STW once (on the next
		// call).
		return int(gcount()), false
	}

	semacquire(&goroutineProfile.sema)

	ourg := getg()

	pcbuf := makeProfStack() // see saveg() for explanation
	stw := stopTheWorld(stwGoroutineProfile)

// goroutines.
//
// Returns the STW context. When starting the world, this context must be
// passed to startTheWorld.
func stopTheWorld(reason stwReason) worldStop {
	semacquire(&worldsema)
	gp := getg()
	gp.m.preemptoff = reason.String()
	systemstack(func() {
		// Mark the goroutine which called stopTheWorld preemptible so its
		// stack may be scanned.