{"record":{"id":"3741c9265e50f932","repo":"rust-lang/rust-analyzer","slug":"failed-to-spawn-thread","errorCode":null,"errorMessage":"failed to spawn thread","messagePattern":"failed to spawn thread","errorType":"panic","errorClass":null,"httpStatus":null,"severity":"error","filePath":"crates/rust-analyzer/src/flycheck.rs","lineNumber":249,"sourceCode":"    ) -> FlycheckHandle {\n        let actor = FlycheckActor::new(\n            id,\n            generation.load(Ordering::Relaxed),\n            sender,\n            config,\n            config_json,\n            sysroot_root,\n            workspace_root,\n            manifest_path,\n            ws_target_dir,\n            ws_build_dir,\n            toolchain_version,\n        );\n        let (sender, receiver) = unbounded::<StateChange>();\n        let thread =\n            stdx::thread::Builder::new(stdx::thread::ThreadIntent::Worker, format!(\"Flycheck{id}\"))\n                .spawn(move || actor.run(receiver))\n                .expect(\"failed to spawn thread\");\n        FlycheckHandle { id, generation, sender, _thread: thread }\n    }\n\n    /// Schedule a re-start of the cargo check worker to do a workspace wide check.\n    pub(crate) fn restart_workspace(&self, saved_file: Option<AbsPathBuf>) {\n        let generation = self.generation.fetch_add(1, Ordering::Relaxed) + 1;\n        self.sender\n            .send(StateChange::Restart {\n                generation,\n                scope: FlycheckScope::Workspace,\n                saved_file,\n                target: None,\n            })\n            .unwrap();\n    }\n\n    /// Schedule a re-start of the cargo check worker to do a package wide check.\n    pub(crate) fn restart_for_package(","sourceCodeStart":231,"sourceCodeEnd":267,"githubUrl":"https://github.com/rust-lang/rust-analyzer/blob/e8f7e90aa3e7b26aa9a000200f606c1078da99ec/crates/rust-analyzer/src/flycheck.rs#L231-L267","documentation":"An `expect` on `stdx::thread::Builder::spawn` in `FlycheckHandle::spawn`: the dedicated flycheck worker thread fails to launch. `std::thread::spawn` essentially only fails on resource exhaustion (thread/process limits, memory), so this indicates the process hit an OS limit while starting the check runner; the input at fault is the OS environment, not flycheck configuration.","triggerScenarios":"Thrown at crates/rust-analyzer/src/flycheck.rs:249 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":["Check `ulimit -u` / cgroup pids.max and raise the thread or process limit for the rust-analyzer process","Reduce concurrent flycheck workspaces so fewer worker threads are needed","Free memory or reduce memory pressure; thread creation fails under exhaustion","Convert the `expect` into a recoverable error so a failed spawn disables flycheck instead of crashing the server"],"exampleFix":null,"handlingStrategy":"retry","validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"e8f7e90aa3e7b26aa9a000200f606c1078da99ec","analyzedAt":"2026-09-03T21:08:06.959Z","contentChangedAt":"2026-09-03T21:08:06.959Z","schemaVersion":2},"datasetVersion":"2026-09-11T07:07:21.782Z"}