1 files changed, 214 insertions, 0 deletions
diff --git a/libgo/go/runtime/lockrank_on.go b/libgo/go/runtime/lockrank_on.go
new file mode 100644
index 0000000..fbc5ff5
--- /dev/null
+++ b/libgo/go/runtime/lockrank_on.go
@@ -0,0 +1,214 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build goexperiment.staticlockranking
+
+package runtime
+
+import (
+	"unsafe"
+)
+
+// lockRankStruct is embedded in mutex
+type lockRankStruct struct {
+	// static lock ranking of the lock
+	rank lockRank
+	// pad field to make sure lockRankStruct is a multiple of 8 bytes, even on
+	// 32-bit systems.
+	pad int
+}
+
+// init checks that the partial order in lockPartialOrder fits within the total
+// order determined by the order of the lockRank constants.
+func init() {
+	for rank, list := range lockPartialOrder {
+		for _, entry := range list {
+			if entry > lockRank(rank) {
+				println("lockPartial order row", lockRank(rank).String(), "entry", entry.String())
+				throw("lockPartialOrder table is inconsistent with total lock ranking order")
+			}
+		}
+	}
+}
+
+func lockInit(l *mutex, rank lockRank) {
+	l.rank = rank
+}
+
+func getLockRank(l *mutex) lockRank {
+	return l.rank
+}
+
+// The following functions are the entry-points to record lock
+// operations.
+// All of these are nosplit and switch to the system stack immediately
+// to avoid stack growths. Since a stack growth could itself have lock
+// operations, this prevents re-entrant calls.
+
+// lockWithRank is like lock(l), but allows the caller to specify a lock rank
+// when acquiring a non-static lock.
+//go:nosplit
+func lockWithRank(l *mutex, rank lockRank) {
+	if l == &debuglock || l == &paniclk {
+		// debuglock is only used for println/printlock(). Don't do lock
+		// rank recording for it, since print/println are used when
+		// printing out a lock ordering problem below.
+		//
+		// paniclk has an ordering problem, since it can be acquired
+		// during a panic with any other locks held (especially if the
+		// panic is because of a directed segv), and yet also allg is
+		// acquired after paniclk in tracebackothers()). This is a genuine
+		// problem, so for now we don't do lock rank recording for paniclk
+		// either.
+		lock2(l)
+		return
+	}
+	if rank == 0 {
+		rank = lockRankLeafRank
+	}
+	gp := getg()
+	// Log the new class.
+	systemstack(func() {
+		i := gp.m.locksHeldLen
+		if i >= len(gp.m.locksHeld) {
+			throw("too many locks held concurrently for rank checking")
+		}
+		gp.m.locksHeld[i].rank = rank
+		gp.m.locksHeld[i].lockAddr = uintptr(unsafe.Pointer(l))
+		gp.m.locksHeldLen++
+
+		// i is the index of the lock being acquired
+		if i > 0 {
+			checkRanks(gp, gp.m.locksHeld[i-1].rank, rank)
+		}
+		lock2(l)
+	})
+}
+
+// acquireLockRank acquires a rank which is not associated with a mutex lock
+//go:nosplit
+func acquireLockRank(rank lockRank) {
+	gp := getg()
+	// Log the new class.
+	systemstack(func() {
+		i := gp.m.locksHeldLen
+		if i >= len(gp.m.locksHeld) {
+			throw("too many locks held concurrently for rank checking")
+		}
+		gp.m.locksHeld[i].rank = rank
+		gp.m.locksHeld[i].lockAddr = 0
+		gp.m.locksHeldLen++
+
+		// i is the index of the lock being acquired
+		if i > 0 {
+			checkRanks(gp, gp.m.locksHeld[i-1].rank, rank)
+		}
+	})
+}
+
+// checkRanks checks if goroutine g, which has mostly recently acquired a lock
+// with rank 'prevRank', can now acquire a lock with rank 'rank'.
+func checkRanks(gp *g, prevRank, rank lockRank) {
+	rankOK := false
+	if rank < prevRank {
+		// If rank < prevRank, then we definitely have a rank error
+		rankOK = false
+	} else if rank == lockRankLeafRank {
+		// If new lock is a leaf lock, then the preceding lock can
+		// be anything except another leaf lock.
+		rankOK = prevRank < lockRankLeafRank
+	} else {
+		// We've now verified the total lock ranking, but we
+		// also enforce the partial ordering specified by
+		// lockPartialOrder as well. Two locks with the same rank
+		// can only be acquired at the same time if explicitly
+		// listed in the lockPartialOrder table.
+		list := lockPartialOrder[rank]
+		for _, entry := range list {
+			if entry == prevRank {
+				rankOK = true
+				break
+			}
+		}
+	}
+	if !rankOK {
+		printlock()
+		println(gp.m.procid, " ======")
+		for j, held := range gp.m.locksHeld[:gp.m.locksHeldLen] {
+			println(j, ":", held.rank.String(), held.rank, unsafe.Pointer(gp.m.locksHeld[j].lockAddr))
+		}
+		throw("lock ordering problem")
+	}
+}
+
+//go:nosplit
+func unlockWithRank(l *mutex) {
+	if l == &debuglock || l == &paniclk {
+		// See comment at beginning of lockWithRank.
+		unlock2(l)
+		return
+	}
+	gp := getg()
+	systemstack(func() {
+		found := false
+		for i := gp.m.locksHeldLen - 1; i >= 0; i-- {
+			if gp.m.locksHeld[i].lockAddr == uintptr(unsafe.Pointer(l)) {
+				found = true
+				copy(gp.m.locksHeld[i:gp.m.locksHeldLen-1], gp.m.locksHeld[i+1:gp.m.locksHeldLen])
+				gp.m.locksHeldLen--
+				break
+			}
+		}
+		if !found {
+			println(gp.m.procid, ":", l.rank.String(), l.rank, l)
+			throw("unlock without matching lock acquire")
+		}
+		unlock2(l)
+	})
+}
+
+// releaseLockRank releases a rank which is not associated with a mutex lock
+//go:nosplit
+func releaseLockRank(rank lockRank) {
+	gp := getg()
+	systemstack(func() {
+		found := false
+		for i := gp.m.locksHeldLen - 1; i >= 0; i-- {
+			if gp.m.locksHeld[i].rank == rank && gp.m.locksHeld[i].lockAddr == 0 {
+				found = true
+				copy(gp.m.locksHeld[i:gp.m.locksHeldLen-1], gp.m.locksHeld[i+1:gp.m.locksHeldLen])
+				gp.m.locksHeldLen--
+				break
+			}
+		}
+		if !found {
+			println(gp.m.procid, ":", rank.String(), rank)
+			throw("lockRank release without matching lockRank acquire")
+		}
+	})
+}
+
+//go:nosplit
+func lockWithRankMayAcquire(l *mutex, rank lockRank) {
+	gp := getg()
+	if gp.m.locksHeldLen == 0 {
+		// No possibilty of lock ordering problem if no other locks held
+		return
+	}
+
+	systemstack(func() {
+		i := gp.m.locksHeldLen
+		if i >= len(gp.m.locksHeld) {
+			throw("too many locks held concurrently for rank checking")
+		}
+		// Temporarily add this lock to the locksHeld list, so
+		// checkRanks() will print out list, including this lock, if there
+		// is a lock ordering problem.
+		gp.m.locksHeld[i].rank = rank
+		gp.m.locksHeld[i].lockAddr = uintptr(unsafe.Pointer(l))
+		gp.m.locksHeldLen++
+		checkRanks(gp, gp.m.locksHeld[i-1].rank, rank)
+		gp.m.locksHeldLen--
+	})
+}