#POSIX Polling — poll Backend

#define FIO_POLL_ENGINE_POLL
#define FIO_POLL
#include "fio-stl.h"

Implementation of the portable polling API on top of POSIX poll() / Windows WSAPoll. This is the fallback backend and is selected automatically when neither epoll nor kqueue is available.

The public API is documented in 102 poll api.md. This file describes backend-specific behavior.

#Backend Details

#struct fio_poll_s

struct fio_poll_s {
  fio_poll_settings_s settings;
  fio___poll_map_s map;
  FIO___LOCK_TYPE lock;
};

The poll backend keeps monitored descriptors in an internal imap (fio___poll_map_s) and takes a snapshot before each poll() call. Descriptors added or re-armed during fio_poll_review are merged with surviving one-shot flags when the call returns.

Do not rely on fio_poll_forget from another thread to cancel a descriptor that is already inside the in-flight snapshot: if the descriptor does not fire, the surviving snapshot entry can be merged back.

#fio_poll_engine

Returns "poll".

#fio_poll_close_all

SFUNC void fio_poll_close_all(fio_poll_s *p);

Additional helper available only in the poll backend. Closes every monitored socket and calls on_close for each one. Useful during shutdown.

#Notes

• POLLRDHUP is used when available; otherwise the backend relies on POLLHUP, POLLERR, and POLLNVAL for close/error detection.
• On Windows, POLLPRI is omitted because WSAPoll rejects it.
• Fired events are stripped from the descriptor’s flags (one-shot semantics). Surviving flags are merged back into the poll set after poll() returns; additions / re-arms merge cleanly, while concurrent removals of in-flight snapshot entries are not a cancellation guarantee.