gcd-operations SKILL.md skillA
gcd-operations from rusel95/ios-agent-skills is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add rusel95/ios-agent-skills/gcd-operations@v1.0.3Pins v1.0.3 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- rusel95/ios-agent-skills
- Path
skills/gcd-operations/SKILL.md- Versions recorded
- 5
- Latest version
- v1.0.3, committed Apr 16, 2026
- First version recorded
- Mar 28, 2026
- Size
- 11,023 bytes
- Repository stars
- 12
- License
- MIT
Use for iOS/macOS concurrency problems involving dispatch queues, locks, or thread safety. Triggers on: deadlocks (sync on main, nested sync, ABBA lock ordering), thread explosion from too many DispatchQueue.global() calls, data races flagged by Thread Sanitizer (TSan), DispatchGroup enter/leave imbalance, DispatchSource timer leaks, lock selection (NSLock vs OSAllocatedUnfairLock vs os_unfair_lock), reader-writer barriers, AsyncOperation subclasses, dispatchPrecondition usage, and…
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# GCD & OperationQueue Concurrency Enterprise-grade concurrency skill for Grand Central Dispatch and OperationQueue. Opinionated: prescribes serial queues by default, target queue hierarchies, labeled queues, `NSLock`/`OSAllocatedUnfairLock` for synchronization, barrier-based reader-writer on custom concurrent queues, and OperationQueue for dependency graphs. Apple has **not deprecated any core GCD APIs** — GCD remains appropriate for parallelism, system I/O, and performance-critical paths. This skill covers correct usage, deadly bug prevention, and coexistence with Swift Concurrency. ## Concurrency Layers ```text Application Layer -> OperationQueue for dependency graphs, cancellation, throttling. Dispatch Layer -> Serial queues for state protection, concurrent+barrier for R/W. Synchronization -> NSLock / OSAllocatedUnfairLock for short critical sections. System I/O -> DispatchSource (timers, file monitoring), DispatchIO (non-blocking file I/O). Thread Pool -> GCD manages threads. App targets 3-4 well-defined queue subsystems. ``` ## Quick Decision Trees ### "Which queue type should I use?" ``` …
Read the whole file at its exact version.
How to install
mdr add rusel95/ios-agent-skills/gcd-operations@sha256:172783882d7e9aeaThe line at the top of this page pins the label v1.0.3, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_3tay4ea7dsgphvjq)
2 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 5 versions of this file, between Mar 28, 2026 and Apr 16, 2026, about one every 5 days.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| v1.0.3 latest | 2026-04-16 | b28e891 | 11,023 B | A | view · diff |
| v1.0.3 | 2026-04-15 | 1b84388 | 11,059 B | A | view · diff |
| v1.0.3 | 2026-04-12 | a0a75d3 | 11,063 B | A | view · diff |
| v1.0.2 | 2026-04-02 | bfdb429 | 11,040 B | A | view · diff |
| v1.0.2 | 2026-03-28 | a3d2425 | 10,976 B | A | view |
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (11023 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
rusel95/ios-agent-skills · 12 stars · license MIT · pushed 2026-10-13 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_3tay4ea7dsgphvjq GET https://markdownregistry.com/api/v1/resolve?ref=rusel95/ios-agent-skills/gcd-operations GET https://markdownregistry.com/api/v1/blob/172783882d7e9aea5f451a99d5a3ccaff39e8d7eda6afb085b7d5d85d528a500
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.