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.

HardTechnical

47 practiced

Describe how process credentials (real/effective UID/GID) interact with execve(2) and setuid/setgid bits. Explain the security model for setuid binaries, how interpreters and shebang lines affect setuid behavior, and SRE operational recommendations when running third-party binaries that require elevated privileges.

HardTechnical

46 practiced

Signals are tricky to get right. Explain SA_RESTART semantics, which syscalls may still return EINTR even with SA_RESTART, reentrancy concerns in signal handlers, and recommended patterns for servers that need to log, emit metrics, and gracefully terminate while avoiding deadlocks or inconsistent state.

EasyTechnical

61 practiced

Explain the difference between a user-space function call and a system call on Linux/x86-64. Describe what happens during the kernel-user boundary transition: which instruction(s) are used, the register calling convention for arguments/return, how context changes, and why system calls are more expensive than normal calls. As an SRE, explain why syscall overhead matters when designing low-latency/high-throughput services and which measurements you would collect to validate impact.

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.

HardTechnical

51 practiced

Explain how futex(2) works under the hood on Linux: describe the userspace fast-path, when the kernel futex wait/wake is invoked, wait-queue semantics, and how futexes appear in strace output. How would you diagnose a system where many threads are blocked in FUTEX_WAIT and latency spikes occur?

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