diff --git a/internal/lsp/debounce.go b/internal/lsp/debounce.go
index 80cf78b48e..06f411471c 100644
--- a/internal/lsp/debounce.go
+++ b/internal/lsp/debounce.go
@@ -9,73 +9,63 @@ import (
 	"time"
 )
 
-type debounceFunc struct {
+type debounceEvent struct {
 	order uint64
 	done  chan struct{}
 }
 
 type debouncer struct {
-	mu    sync.Mutex
-	funcs map[string]*debounceFunc
+	mu     sync.Mutex
+	events map[string]*debounceEvent
 }
 
 func newDebouncer() *debouncer {
 	return &debouncer{
-		funcs: make(map[string]*debounceFunc),
+		events: make(map[string]*debounceEvent),
 	}
 }
 
-// debounce waits timeout before running f, if no subsequent call is made with
-// the same key in the intervening time. If a later call to debounce with the
-// same key occurs while the original call is blocking, the original call will
-// return immediately without running its f.
-//
-// If order is specified, it will be used to order calls logically, so calls
-// with lesser order will not cancel calls with greater order.
-func (d *debouncer) debounce(key string, order uint64, timeout time.Duration, f func()) {
-	if timeout == 0 {
-		// Degenerate case: no debouncing.
-		f()
-		return
-	}
+// debounce returns a channel that receives a boolean reporting whether,
+// by the time the delay channel receives a value, this call is (or will be)
+// the most recent call with the highest order number for its key.
+func (d *debouncer) debounce(key string, order uint64, delay <-chan time.Time) <-chan bool {
+	okc := make(chan bool, 1)
 
-	// First, atomically acquire the current func, cancel it, and insert this
-	// call into d.funcs.
 	d.mu.Lock()
-	current, ok := d.funcs[key]
-	if ok && current.order > order {
-		// If we have a logical ordering of events (as is the case for snapshots),
-		// don't overwrite a later event with an earlier event.
-		d.mu.Unlock()
-		return
-	}
-	if ok {
-		close(current.done)
+	if prev, ok := d.events[key]; ok {
+		if prev.order > order {
+			// If we have a logical ordering of events (as is the case for snapshots),
+			// don't overwrite a later event with an earlier event.
+			d.mu.Unlock()
+			okc <- false
+			return okc
+		}
+		close(prev.done)
 	}
 	done := make(chan struct{})
-	next := &debounceFunc{
+	next := &debounceEvent{
 		order: order,
 		done:  done,
 	}
-	d.funcs[key] = next
+	d.events[key] = next
 	d.mu.Unlock()
 
-	// Next, wait to be cancelled or for our wait to expire. There is a race here
-	// that we must handle: our timer could expire while another goroutine holds
-	// d.mu.
-	select {
-	case <-done:
-	case <-time.After(timeout):
-		d.mu.Lock()
-		if d.funcs[key] != next {
-			// We lost the race: another event has arrived for the key and started
-			// waiting. We could reasonably choose to run f at this point, but doing
-			// nothing is simpler.
+	go func() {
+		ok := false
+		select {
+		case <-delay:
+			d.mu.Lock()
+			if d.events[key] == next {
+				ok = true
+				delete(d.events, key)
+			} else {
+				// The event was superseded before we acquired d.mu.
+			}
 			d.mu.Unlock()
-			return
+		case <-done:
 		}
-		delete(d.funcs, key)
-		d.mu.Unlock()
-		f()
-	}
+		okc <- ok
+	}()
+
+	return okc
 }
diff --git a/internal/lsp/debounce_test.go b/internal/lsp/debounce_test.go
index 0712d6f284..b5597faf59 100644
--- a/internal/lsp/debounce_test.go
+++ b/internal/lsp/debounce_test.go
@@ -5,25 +5,16 @@
 package lsp
 
 import (
-	"fmt"
-	"strings"
-	"sync"
 	"testing"
 	"time"
-
-	errors "golang.org/x/xerrors"
 )
 
 func TestDebouncer(t *testing.T) {
 	t.Parallel()
 
-	const evtWait = 30 * time.Millisecond
-	const initialDelay = 400 * time.Millisecond
-
 	type event struct {
 		key       string
 		order     uint64
-		fired     bool
 		wantFired bool
 	}
 	tests := []struct {
@@ -65,72 +56,26 @@ func TestDebouncer(t *testing.T) {
 	for _, test := range tests {
 		test := test
 		t.Run(test.label, func(t *testing.T) {
-			try := func(delay time.Duration) (bool, error) {
-				d := newDebouncer()
-				var wg sync.WaitGroup
-				var validMu sync.Mutex
-				valid := true
-				prev := -1
-				for i, e := range test.events {
-					wg.Add(1)
-					go func(i int, e *event) {
-						// Check if goroutines were not scheduled in the intended order.
-						validMu.Lock()
-						if prev != i-1 {
-							valid = false
-						}
-						prev = i
-						validMu.Unlock()
+			d := newDebouncer()
 
-						d.debounce(e.key, e.order, delay, func() {
-							e.fired = true
-						})
-						wg.Done()
-					}(i, e)
-					// For a bit more fidelity, sleep to try to make things actually
-					// execute in order. This shouldn't have to be perfect: as long as we
-					// don't have extreme pauses the test should still pass.
-					if i < len(test.events)-1 {
-						time.Sleep(evtWait)
-					}
-				}
-				wg.Wait()
+			delays := make([]chan time.Time, len(test.events))
+			okcs := make([]<-chan bool, len(test.events))
 
-				var errs []string
-				for _, event := range test.events {
-					if event.fired != event.wantFired {
-						msg := fmt.Sprintf("(key: %q, order: %d): fired = %t, want %t",
-							event.key, event.order, event.fired, event.wantFired)
-						errs = append(errs, msg)
-					}
-				}
-				var err error
-				if len(errs) > 0 {
-					err = errors.New(strings.Join(errs, "\n"))
-				}
-				return valid, err
+			// Register the events in deterministic order, synchronously.
+			for i, e := range test.events {
+				delays[i] = make(chan time.Time, 1)
+				okcs[i] = d.debounce(e.key, e.order, delays[i])
 			}
 
-			if err := retryInvalid(initialDelay, try); err != nil {
-				t.Error(err)
+			// Now see which event fired.
+			for i, okc := range okcs {
+				event := test.events[i]
+				delays[i] <- time.Now()
+				fired := <-okc
+				if fired != event.wantFired {
+					t.Errorf("[key: %q, order: %d]: fired = %t, want %t", event.key, event.order, fired, event.wantFired)
+				}
 			}
 		})
 	}
 }
-
-// retryInvalid runs the try func up to three times with exponential back-off
-// in its duration argument, starting with the provided initial duration. Calls
-// to try are retried if their first result indicates that they may be invalid,
-// and their second result is a non-nil error.
-func retryInvalid(initial time.Duration, try func(time.Duration) (valid bool, err error)) (err error) {
-	delay := initial
-	for attempts := 3; attempts > 0; attempts-- {
-		var valid bool
-		valid, err = try(delay)
-		if err == nil || valid {
-			return err
-		}
-		delay += delay
-	}
-	return err
-}
diff --git a/internal/lsp/diagnostics.go b/internal/lsp/diagnostics.go
index d3f8c8ad40..ef23372932 100644
--- a/internal/lsp/diagnostics.go
+++ b/internal/lsp/diagnostics.go
@@ -12,6 +12,7 @@ import (
 	"path/filepath"
 	"strings"
 	"sync"
+	"time"
 
 	"golang.org/x/tools/internal/event"
 	"golang.org/x/tools/internal/lsp/debug/log"
@@ -119,10 +120,10 @@ func (s *Server) diagnoseSnapshot(snapshot source.Snapshot, changedURIs []span.U
 		// delay.
 		s.diagnoseChangedFiles(ctx, snapshot, changedURIs, onDisk)
 		s.publishDiagnostics(ctx, false, snapshot)
-		s.diagDebouncer.debounce(snapshot.View().Name(), snapshot.ID(), delay, func() {
+		if ok := <-s.diagDebouncer.debounce(snapshot.View().Name(), snapshot.ID(), time.After(delay)); ok {
 			s.diagnose(ctx, snapshot, false)
 			s.publishDiagnostics(ctx, true, snapshot)
-		})
+		}
 		return
 	}
 
diff --git a/internal/lsp/text_synchronization.go b/internal/lsp/text_synchronization.go
index 6ebab4f115..f54ca3735c 100644
--- a/internal/lsp/text_synchronization.go
+++ b/internal/lsp/text_synchronization.go
@@ -9,6 +9,7 @@ import (
 	"context"
 	"fmt"
 	"path/filepath"
+	"time"
 
 	"golang.org/x/tools/internal/event"
 	"golang.org/x/tools/internal/jsonrpc2"
@@ -241,7 +242,11 @@ func (s *Server) didModifyFiles(ctx context.Context, modifications []source.File
 	//     process changes in order.
 	s.pendingOnDiskChanges = append(s.pendingOnDiskChanges, pending)
 	ctx = xcontext.Detach(ctx)
-	delayed := func() {
+	okc := s.watchedFileDebouncer.debounce("", 0, time.After(delay))
+	go func() {
+		if ok := <-okc; !ok {
+			return
+		}
 		s.fileChangeMu.Lock()
 		var allChanges []source.FileModification
 		// For accurate progress notifications, we must notify all goroutines
@@ -263,8 +268,7 @@ func (s *Server) didModifyFiles(ctx context.Context, modifications []source.File
 		for _, done := range dones {
 			close(done)
 		}
-	}
-	go s.watchedFileDebouncer.debounce("", 0, delay, delayed)
+	}()
 	return nil
 }