vecstore: disable deadlock linting for inMemoryLock

Do not use syncutil.RWMutex in the inMemoryLock class, because deadlock
detection reports spurious failures. Different partitions in the vector
index can be locked in different orders by merge, split, format and other
operations. In all these cases, we first acquire the in-memory store's
structure lock to prevent deadlocks. But the deadlock detection package
is not smart enough to realize this and reports false positives.

Epic: CRDB-42943

Release note: None

pkg/sql/vecindex/vecstore/in_memory_lock.go

@@ -6,16 +6,22 @@
 package vecstore
 
 import (
+	"sync"
 	"sync/atomic"
-
-	"github.com/cockroachdb/cockroach/pkg/util/syncutil"
 )
 
 // inMemoryLock wraps a read-write lock, adding support for reentrancy and
 // ownership tracking.
+// NOTE: This is only used in testing and benchmarking code.
 type inMemoryLock struct {
 	mu struct {
-		syncutil.RWMutex
+		// NOTE: Do not use syncutil.RWMutex here, because deadlock detection
+		// reports spurious failures. Different partitions in the vector index
+		// can be locked in different orders by merge, split, format and other
+		// operations. In all these cases, we first acquire the in-memory store's
+		// structure lock to prevent deadlocks. But the deadlock detection package
+		// is not smart enough to realize this and reports false positives.
+		sync.RWMutex
 
 		// reentrancy counts how many times the same owner has acquired the same
 		// lock.

pkg/testutils/lint/lint_test.go

@@ -758,6 +758,8 @@ func TestLint(t *testing.T) {
 			":!testutils/lint/passes/deferunlockcheck/testdata/src/github.com/cockroachdb/cockroach/pkg/util/syncutil/mutex_sync.go",
 			// Exception needed for goroutineStalledStates.
 			":!kv/kvserver/concurrency/concurrency_manager_test.go",
+			// See comment in inMemoryLock class.
+			":!sql/vecindex/vecstore/in_memory_lock.go",
 		)
 		if err != nil {
 			t.Fatal(err)