Receiving an SCM_RIGHTS message creates descriptor references that your process must either accept into a defined owner or close on every rejection path. It does not transfer the sender’s descriptor number, revoke the sender’s access or guarantee that the application accepted the handle. Treat ancillary parsing and ownership admission as one carefully bounded transaction. This…
Choose eventfd read semantics from the information your consumer must retain. An ordinary eventfd read returns the accumulated counter and clears it. An EFD_SEMAPHORE read returns one and decrements the counter by one. Neither mode carries your work payload or automatically makes a shared queue safe; the queue and its ownership protocol remain authoritative. This…
For an absolute wall-clock timer, treat ECANCELED as a request to reconsider the calendar deadline after a discontinuous clock change. It is not an expiration count and should not trigger the scheduled action automatically. Record the scheduling generation, obtain the current clock context, apply the missed-deadline policy and rearm deliberately. This guide uses Linux man-pages…
Create a signalfd-based control path only after arranging the same blocked signal set in every thread that could otherwise receive those process-directed signals. The simplest startup sequence blocks the set in the initial thread before creating workers, then gives one dispatcher responsibility for reading the signalfd. Creating the descriptor alone does not change anyone’s signal…
An edge-triggered epoll loop must remember readiness until nonblocking I/O establishes that no more progress is currently possible. For fairness, it may stop after a bounded amount of work, but it must keep that source on its own ready list. Stopping early and then sleeping for another edge can strand unread input; draining one busy…
Use a pidfd to keep a stable reference to one process lifetime after acquiring its identity correctly. A numeric PID read later from a stale record can identify a different process after reuse. A pidfd prevents that reference from silently retargeting, but it does not repair an acquisition that already selected the wrong process, grant…
A minimal init or supervisor must retain each child’s termination result while removing the kernel’s waitable record. Treat SIGCHLD as a reason to inspect children, not as a one-signal-per-exit ledger. Assign one reaping owner, drain available statuses, and record the service generation before deciding whether to restart it. This guide uses Linux process semantics documented…
When process or thread creation fails, inspect task-count limits and their hierarchy before blaming free-memory capacity. Linux’s cgroup PID controller counts kernel tasks, including threads. A service with only a few process IDs can still consume its allowance through worker pools and helper activity. This guide uses upstream Linux v6.12 cgroup v2 behavior and Linux…
Correlate service stalls with cgroup CPU-bandwidth enforcement before assuming that the whole machine is overloaded. A group can exhaust its permitted CPU time while other processors are idle. Additional application threads can consume that shared allowance sooner without increasing the amount available during the period. This guide uses upstream Linux v6.12 cgroup v2 interfaces and…
Review the synchronization property each driver path relies on before treating PREEMPT_RT as a configuration-only migration. On the RT kernel, a familiar spinlock or interrupt suffix can have different execution-context behavior. Code that accidentally relied on non-preemptibility may need a deliberate locking or per-CPU ownership change. This guide uses upstream Linux v6.12. It proposes a…