Board-level Linux integration, U-Boot, device trees, kernel drivers and peripheral bring-up. Separate power and hardware checks from software adaptation, and define a recoverable boot path.
Set close-on-exec when a descriptor is created, duplicated or received, unless it belongs to an explicit helper-inheritance contract. Adding FD_CLOEXEC later with fcntl leaves a multithreaded fork/exec window. A helper can retain a device port, socket or pipe after the parent closes its copy, preventing the release the service expected. This guide follows Linux man-pages…
Use discard advice only when the application has explicitly surrendered the affected pages’ contents or can reconstruct them under the mapping’s contract. Linux MADV_DONTNEED can change what later reads return. A successful call is not a promise to preserve a live buffer while merely making its RAM accounting smaller. This guide uses Linux man-pages 6.12…
Authenticate a local socket client using kernel-supplied credentials at the boundary your authorization policy actually needs. SO_PEERCRED supplies a connection-related snapshot; it is not a continuously refreshed statement about whoever currently writes each byte. If authority must follow each message, evaluate message credentials and an explicit protocol instead of assuming a connected descriptor permanently identifies…
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…