work.cpuStats.accumulateGCPauseTime(nanotime()-stw.finishedStopping, work.maxprocs)

	// Concurrent mark.
	systemstack(func() {
		now = startTheWorldWithSema(0, stw)
		work.pauseNS += now - stw.startedStopping
		work.tMark = now

		// Release the CPU limiter.
		gcCPULimiter.finishGCTransition(now)
	})

	// Release the world sema before Gosched() in STW mode

		// 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)

//
// If flags&gcDrainFlushBgCredit != 0, gcDrain flushes scan work
// credit to gcController.bgScanCredit every gcCreditSlack units of
// scan work.
//
// gcDrain will always return if there is a pending STW or forEachP.
//
// Disabling write barriers is necessary to ensure that after we've
// confirmed that we've drained gcw, that we don't accidentally end
// up flipping that condition by immediately adding work in the form

	// allspans is a slice of all mspans ever created. Each mspan
	// appears exactly once.
	//
	// The memory for allspans is manually managed and can be
	// reallocated and move as the heap grows.
	//
	// In general, allspans is protected by mheap_.lock, which
	// prevents concurrent access as well as freeing the backing
	// store. Accesses during STW might not hold the lock, but

	bgScanCredit atomic.Int64

	// assistTime is the nanoseconds spent in mutator assists
	// during this cycle. This is updated atomically, and must also
	// be updated atomically even during a STW, because it is read
	// by sysmon. Updates occur in bounded batches, since it is both
	// written and read throughout the cycle.
	assistTime atomic.Int64

			// CMP Rarg0, $0
			// BNE 2(PC)
			// STW R0, 0(R0)
			// NOP (so the BNE has somewhere to land)

			// CMP Rarg0, $0
			p := s.Prog(ppc64.ACMP)
			p.From.Type = obj.TYPE_REG
			p.From.Reg = v.Args[0].Reg()
			p.To.Type = obj.TYPE_CONST
			p.To.Offset = 0

			// BNE 2(PC)
			p2 := s.Prog(ppc64.ABNE)
			p2.To.Type = obj.TYPE_BRANCH

			// STW R0, 0(R0)

	go122.EvGoSyscallEnd:        (*ordering).advanceGoSyscallEnd,
	go122.EvGoSyscallEndBlocked: (*ordering).advanceGoSyscallEndBlocked,
	go122.EvGoStatus:            (*ordering).advanceGoStatus,

	// STW.
	go122.EvSTWBegin: (*ordering).advanceGoRangeBegin,
	go122.EvSTWEnd:   (*ordering).advanceGoRangeEnd,

	// GC events.
	go122.EvGCActive:           (*ordering).advanceGCActive,