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Marc Schier
1cca744b5c
Closes #4201. Closes #4202. Closes #4203. Closes #4215. Closes #4216. (#4215 and #4216 are @marcschier's originals from the #4188 review; #4202 and #4201 are my later duplicates of the same two findings. All four describe the two changes in section 1 and are closed together.) **This PR now carries what was #4221 as well.** The two were a stack; they have been unstacked and combined here, and #4221 is closed. Everything below the "Read the server diagnostics" section is the work that was previously reviewed as #4221. --- ## 1. The browse path guards itself, and the last node locks are gone `AsyncCustomNodeManager` kept two `lock (source)` sites around `CreateBrowser`, carrying a NOTE that browser creation was not internally synchronized. `NodeBrowser` still handed its lock to derived types through `protected Lock DataLock`. `NodeState.CreateBrowser` now holds a browse lock across `PopulateBrowser` and `OnPopulateBrowser`, so browser construction on a node is serialized — which is what the external `lock (source)` was actually providing, and what a handler that mutates the node during population (the historian's lazy config installer) depends on. Both `lock (source)` statements and the NOTE are gone. **What that lock does not do**, stated plainly in the XML docs and in `docs/NodeManagers.md` rather than over-promised: it is not an atomic snapshot across the node's children, notifiers and references. Writers take those collections' own locks, not the browse lock. The browser is a point-in-time copy and each collection is read consistently, but the combination is not a transaction. No `lock` takes a `NodeState` as its sync root any more. That was the last thing keeping `NodeState` from being documentably self-guarding, so the other eleven went with it: `lock (activeNode)`, `lock (target)`, `lock (source.Node)`, `lock (target.Node)`, `lock (notifier)`, `lock (handle.Node)` in `AsyncCustomNodeManager`, and `lock (node)` in `CustomNodeManager2`. Most were a check-then-act pair now served by `NodeState.AddReferenceIfMissing`, which does the check and the insert under the node's own lock. `NodeBrowser.DataLock` is removed. A browser is **single-consumer**: it belongs to whoever created it, and both server browse paths already serialize on the owning side. The exposed lock only added an inheritance-level locking contract that a derived browser could not reason about. ## 2. Read the server diagnostics under the lock every writer takes `OnUpdateDiagnostics` locked the diagnostics **payload** rather than the lock every writer takes through `UpdateServerDiagnostics`, so the snapshot a client reads from the `ServerDiagnostics` node was never excluded from a concurrent writer. Both halves matter, and the second is the one that is easy to miss: ```csharp lock (m_diagnosticsLock) // was: lock (ServerDiagnostics) { value = Variant.FromStructure(ServerDiagnostics, copy: true); // was: copy defaulted to false } ``` `copy: true` is what makes it a snapshot. `FromStructure(value, copy: false)` does `new ExtensionObject(value, copy)` — it wraps the **live** structure without copying it, so the caller would read the fields long after the lock was released and see them change underneath. Swapping the lock alone would have looked like a fix while still excluding nothing. ## 3. Analyzer numbering The browser rule is **UA0027**, not UA0025. This branch had independently taken UA0025 for `NodeBrowser.DataLock` while #4188 published UA0025 for `ILocalNode.DataLock` and UA0026 for `BaseVariableValue.Lock`. Master's are shipped, so they keep the numbers: | | UA0025 | UA0026 | UA0027 | |---|---|---|---| | master (#4188) | `ILocalNode.DataLock` | `BaseVariableValue.Lock` | — | | **this PR** | `ILocalNode.DataLock` | `BaseVariableValue.Lock` | **`NodeBrowser.DataLock`** | Both sides had written a different `UA0025Tests.cs`, which arrived as an add/add conflict. They are now split: `UA0025Tests.cs` holds master's `ILocalNode` tests, `UA0027Tests.cs` holds the `NodeBrowser` ones. UA0024's help text also drops its reference to `ReadServerDiagnostics`, which #4193 removed as unused, and names `ISession.ReadDiagnostics` / `ISubscription.ReadDiagnostics` instead — those do still exist. ## 4. Two more locks reachable from outside their owner **`ApplicationConfiguration.PropertiesLock` is removed.** It returned the properties dictionary itself, so `lock (configuration.PropertiesLock)` was `lock (configuration.Properties)` — the lock *was* the data it guarded, the same shape as #4203. It had exactly one production consumer (`OAuth2CredentialCollection.Load`, a get-or-add with `ParseExtension` called inside the lock), so it could not simply be deleted. `Properties` is now a `ConcurrentDictionary` — same public type, every operation atomic on its own — and the one multi-operation need gets a member of its own: ```csharp public T GetOrAddProperty<T>(string key, Func<T> valueFactory); ``` It deliberately does **not** invoke the factory under a lock, so `ParseExtension` now runs outside any critical section. Holding a lock across a caller-supplied callback is exactly the shape that produced the attribute/diagnostics deadlock earlier in this work. The two existing tests asserted only `PropertiesLock is not null`, so they tested nothing but its presence. They are replaced by tests of the contract: factory runs once for a missing key, not at all for a present one, 32 concurrent callers all observe the same instance, null arguments throw. `PropertiesLock` ships in 1.5.378, so this is a breaking removal — migration guide section plus analyzer **UA0028**. **`SharedDefinitionCache` no longer hands out its lock.** Three sites in `SharedKeyValueSubscriptionStore` took the nested cache's `Lock` to operate on the cache's own dictionary. Both are private now, behind `ReplaceAll` and `CloneWhere`. `SnapshotCommitLock` stays exposed on purpose: it is a `SemaphoreSlim` sequencing an async commit across `await` points, which `System.Threading.Lock` cannot span, so folding it in would change behaviour rather than hide a lock. ## Verification Merged `master` (`0edfe237a`, including #4234) with no conflicts. - `dotnet build UA.slnx` — 0 warnings, 0 errors - `Opc.Ua.Server.Tests` — 4074 passed - `Opc.Ua.Types.Tests` — 8501 passed - `Opc.Ua.MigrationAnalyzer.Tests` — 151 passed on all five TFMs (138 → 151, the new ones being UA0027 and UA0028) - `Opc.Ua.Core.Tests` — 4249 passed - `Opc.Ua.Redundancy.Server.Tests` — 573 passed ## Note for the reviewer @romanett — your approval was given when this PR's diff was the 7 diagnostics files, because it was measured against `marcschier/node-browse-locks`. Now that the two are combined and the base is `master`, the diff is 23 files, and the extra 16 are the node/browser lock work that was #4221. GitHub kept the approval across the retarget, but it did not cover that code, so please re-review rather than let it ride. --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: e9c13dd0-a6e3-4ad2-8ad6-1c3fe6323041 Copilot-Session: b3c0e146-5b9e-4d08-a0f6-db3f940484b1 Copilot-Session: d18f87e9-2484-44ce-98ce-463ba6cf5f63 Copilot-Session: 0ee22c1d-c319-4257-bf78-a5a077a1824a