Fix checklock errors discovered by #12347

The changes in #12347 led to additional errors being reported in existing code. This PR addresses those issues with additional annotations.

FUTURE_COPYBARA_INTEGRATE_REVIEW=#12379 from uzairnawaz:fix-new-checklock-errors 9871b5a
PiperOrigin-RevId: 844243954

Author: Uzair Nawaz

pkg/tcpip/transport/tcp/endpoint.go

@@ -688,6 +688,7 @@ func (e *Endpoint) LockUser() {
 	// Finally just give up and wait for the Lock.
 	e.mu.Lock()
 	e.ownedByUser.Store(1)
+	return // +checklocksforce: this locks e.snd.ep.mu
 }
 
 // UnlockUser will check if there are any segments already queued for processing
@@ -753,6 +754,7 @@ func (e *Endpoint) AssertLockHeld(locked *Endpoint) {
 	if e != locked {
 		panic("AssertLockHeld failed: locked endpoint != asserting endpoint")
 	}
+	return // +checklocksforce
 }
 
 // TryLock is a helper that calls TryLock on the endpoint's mutex and

tools/checklocks/test/branches.go

@@ -22,6 +22,7 @@ func testInconsistentReturn(tc *oneGuardStruct) { // +checklocksfail
 	if x := rand.Intn(10); x%2 == 1 {
 		tc.mu.Lock()
 	}
+	return
 }
 
 func testConsistentBranching(tc *oneGuardStruct) {
@@ -53,6 +54,7 @@ func testInconsistentBranching(tc *oneGuardStruct) { // +checklocksfail:2
 	if x%2 == 1 {
 		tc.mu.Unlock() // +checklocksforce
 	}
+	return
 }
 
 func testUnboundedLocks(tc []*oneGuardStruct) {

tools/checklocks/test/methods.go

@@ -96,6 +96,7 @@ func standaloneFunctionWithGuard(a *testMethodsWithParameters) {
 	a.guardedField = 1
 	a.mu.Unlock()
 	a.guardedField = 1 // +checklocksfail
+	return             // +checklocksfail
 }
 
 type testMethodsWithEmbedded struct {