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fix(driver-ablegacy): resolve Medium code-review finding (Driver.AbLegacy-007)

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Runtimes and ParentRuntimes changed from Dictionary to ConcurrentDictionary.
EnsureTagRuntimeAsync and EnsureParentRuntimeAsync now use a per-key
GetCreationLock semaphore with a double-checked pattern: fast-path read
requires no lock; slow-path create+initialize+store is serialised per key
so a concurrent caller waits rather than creating a duplicate runtime that
would be leaked when DisposeRuntimes runs.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Joseph Doherty
2026-05-22 09:25:35 -04:00
parent 47eac2d84f
commit 7661d1b5dc
2 changed files with 83 additions and 34 deletions
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code-reviews/Driver.AbLegacy/findings.md
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@@ -194,7 +194,7 @@ shared libplctag `Tag` handle is never touched by two threads at once.
| Severity | Medium |
| Category | Concurrency & thread safety |
| Location | `AbLegacyDriver.cs:411-438`, `AbLegacyDriver.cs:386-409` |
| Status | Open |
| Status | Resolved |
**Description:** `EnsureTagRuntimeAsync` and `EnsureParentRuntimeAsync` are
check-then-act: `device.Runtimes.TryGetValue(...)` then, after `await
@@ -209,7 +209,7 @@ corrupt internal state. `ParentRuntimes` has the identical pattern.
`GetOrAdd`, or guard runtime creation under a per-device lock. Ensure the losing
runtime of any race is disposed.
**Resolution:** _(open)_
**Resolution:** Resolved 2026-05-22 — `Runtimes` and `ParentRuntimes` changed to `ConcurrentDictionary`; `EnsureTagRuntimeAsync` and `EnsureParentRuntimeAsync` now hold a per-key `GetCreationLock` semaphore around the double-checked create+initialize+store sequence so exactly one runtime is created per key and no race-loser is leaked.
### Driver.AbLegacy-008