{"record":{"id":"33da26fcb90905a1","repo":"firecracker-microvm/firecracker","slug":"timerfd-read-failed-err","errorCode":null,"errorMessage":"TimerFd read failed: {err:#}","messagePattern":"TimerFd read failed: (.+?)","errorType":"panic","errorClass":null,"httpStatus":null,"severity":"error","filePath":"src/utils/src/time.rs","lineNumber":252,"sourceCode":"            },\n        };\n        // SAFETY: Safe because this doesn't modify any memory and we check the return value.\n        let ret = unsafe { libc::timerfd_settime(self.as_raw_fd(), 0, &spec, ptr::null_mut()) };\n        assert!(\n            0 <= ret,\n            \"TimerFd arm failed: {:#}\",\n            std::io::Error::last_os_error()\n        );\n    }\n\n    /// Read the value from the timerfd. Since it is always created with NONBLOCK flag,\n    /// this function does not block.\n    pub fn read(&mut self) -> u64 {\n        let mut buf = [0u8; size_of::<u64>()];\n        match self.0.read(buf.as_mut_slice()) {\n            Ok(_) => u64::from_ne_bytes(buf),\n            Err(inner) if inner.kind() == ErrorKind::WouldBlock => 0,\n            Err(err) => panic!(\"TimerFd read failed: {err:#}\"),\n        }\n    }\n\n    /// Tell if the timer is currently armed.\n    pub fn is_armed(&self) -> bool {\n        // SAFETY: Zero init of a PDO type.\n        let mut spec: libc::itimerspec = unsafe { std::mem::zeroed() };\n        // SAFETY: Safe because timerfd_gettime is trusted to only modify `spec`.\n        let ret = unsafe { libc::timerfd_gettime(self.as_raw_fd(), &mut spec) };\n        assert!(\n            0 <= ret,\n            \"TimerFd arm failed: {:#}\",\n            std::io::Error::last_os_error()\n        );\n        spec.it_value.tv_sec != 0 || spec.it_value.tv_nsec != 0\n    }\n}\n","sourceCodeStart":234,"sourceCodeEnd":270,"githubUrl":"https://github.com/firecracker-microvm/firecracker/blob/0a745def42ddf4cc2a744d79a08a27ff50b5d27a/src/utils/src/time.rs#L234-L270","documentation":"Error \"TimerFd read failed: {err:#}\" thrown in firecracker-microvm/firecracker.","triggerScenarios":"Thrown at src/utils/src/time.rs:252 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":["Check that the timerfd was created successfully and not closed before read.","Handle EAGAIN on non-blocking timerfd reads and re-arm the timer correctly."],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"0a745def42ddf4cc2a744d79a08a27ff50b5d27a","analyzedAt":"2026-08-19T05:27:02.517Z","contentChangedAt":"2026-08-19T05:27:02.517Z","schemaVersion":2},"datasetVersion":"2026-09-14T00:17:10.932Z"}