Linux
23 Sep 2026
4 min read
signalfd Consumes Blocked Signals Through File Descriptor Reads
signalfd Consumes Blocked Signals Through File Descriptor Reads signalfd() turns selected signal notifications into records that can be consumed with read(). A matching pending signal makes the descriptor readable, which allows signal handling to share the same poll(), select(), or epoll path as sockets, timers, and other descriptors. The descriptor does not redirect signals merely because its mask names them. Normal signal-mask rules still apply. In the usual design, the selected signals are blocked before they can be delivered through their ordinary dispositions, then a signalfd reads the pending instances.