Process Management

Linux 20 Sep 2026 5 min read

pidfd_getfd Duplicates a Live File Descriptor Across Processes

A process can acquire a usable duplicate of a file descriptor that is already open in another process without asking that process to send it over a UNIX domain socket. Linux pidfd_getfd() performs that transfer through a PID file descriptor, subject to a ptrace access check. The returned descriptor is new in the caller, but the kernel object behind it is not independent. It refers to the same open file description as the target descriptor. That distinction controls offset sharing, file status flags, and operations on the underlying object.

Linux pidfd

Linux 19 Sep 2026 6 min read

process_madvise Applies Memory Advice Across Process Boundaries

A process can consume memory on behalf of work that is coordinated elsewhere. Linux process_madvise() lets that external coordinator apply selected virtual-memory advice to ranges in the target process without injecting code into it. The target is identified by a pidfd, while the ranges are supplied as an array of struct iovec. That arrangement separates memory-policy decisions from the code that owns the mapping. A runtime manager, service supervisor, or memory controller can request reclaim-oriented or prefetch-oriented treatment for another process, subject to kernel support and permission checks. The system call does not transfer ownership of the mapping, freeze the target, or make its address space stable.

Software Engineering Linux

Software Engineering 18 Sep 2026 8 min read

Linux close_range Makes Descriptor-Table Cleanup a Range Operation

A process preparing to execute another program often needs a simple descriptor invariant: standard input, output, and error remain available, while unrelated descriptors do not cross the execution boundary. Closing descriptors one at a time can turn that invariant into an enumeration problem. Linux close_range() instead applies an operation to an inclusive numeric interval in the calling task’s file-descriptor table. The interface is small, but its semantics reach into descriptor-table sharing, execve() inheritance, concurrent descriptor allocation, and privilege transitions. The flags select more than implementation strategy: they determine whether descriptors disappear immediately, become close-on-exec, or are first separated from a table shared with other tasks.

Software Engineering Linux

Linux 18 Sep 2026 6 min read

close_range Controls Descriptor Inheritance Across exec Boundaries

A process preparing to call execve() may have hundreds or thousands of open file descriptors, while the new program should inherit only a small selected set. Closing descriptors one by one creates both bookkeeping cost and a concurrency problem: another thread can allocate a descriptor while the cleanup loop is still running. Linux close_range() moves that operation to the descriptor-table boundary. A caller specifies an inclusive numeric range and asks the kernel either to close descriptors in that range or mark them close-on-exec. With CLOSE_RANGE_UNSHARE, the caller can first detach its descriptor table from threads or processes that share it.

Linux System Calls