System Calls Fundamentals Questions
Core OS-level concepts covering system call interfaces and conventions, examples such as fork, exec, opendir, and stat, kernel-user space interactions, process lifecycle, file I/O, memory management primitives, and basic concurrency primitives in systems programming.
EasyTechnical
51 practiced
Discuss how errno is set by system calls on failure, the thread-safety concerns of strerror(3) vs strerror_r(3), and best practices for formatting diagnostic messages in SRE-run services (include syscall name, errno numeric value, and human-readable text). Also cover minimal-impact ways to collect such errors in high-throughput paths.
HardTechnical
50 practiced
Describe TOCTOU (time-of-check to time-of-use) race conditions when performing file system operations. Provide concrete examples where checking a path then opening it leads to vulnerabilities. Explain how openat(2), O_NOFOLLOW, O_DIRECTORY, and fstatat(2) can be used to avoid races and perform secure atomic checks and opens.
MediumTechnical
68 practiced
A worker process keeps being killed by the OOM killer on your Linux host. Explain how setrlimit(2) can be used to constrain memory usage per process and the differences between RLIMIT_AS and RLIMIT_RSS. Discuss consequences of overly strict limits and how you would choose sensible limits for a service while preserving reliability and SLOs.
MediumTechnical
55 practiced
Explain how sendfile(2), splice(2), and tee(2) enable zero-copy or reduced-copy data transfer on Linux. For each syscall describe typical use-cases (file->socket, pipe->socket, duplicating data) and limitations (supported fd types, blocking behavior). From an SRE perspective, when would using these APIs be beneficial and what monitoring signals indicate improvements?
HardTechnical
57 practiced
A high-performance server has high context-switch rates and increased user CPU because it issues many small read/write syscalls. Propose actionable strategies to reduce context switches and syscall count (for example, batching, writev/readv, user-space buffering, zero-copy APIs), explain trade-offs in latency vs throughput, and outline how you would benchmark and validate improvements in production.
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