LIO_LISTIO(2)

📦 version 15.1, in freebsd 14.5, freebsd 15.1

🌸 NAME 🌸

hey bestie 💖 welcome to the LIO_LISTIO(2) page — this is the System Calls Manual, and we're literally about to get into lio_listio — list directed I/O (REALTIME). it's giving syscall main character energy, no cap ✨

📚 LIBRARY 📚

Standard C Library (libc, -lc) — yes bestie, the classic 💅

🦋 SYNOPSIS 🦋

#include <aio.h>

int
lio_listio(int mode, struct aiocb * const list[], int nent,
    struct sigevent *sig);

✨ DESCRIPTION ✨

okay so the lio_listio() function initiates a list of I/O requests with a single function call. iconic behavior, honestly 🫶 the list argument is an array of pointers to aiocb structures describing each operation to perform, with nent elements. NULL elements are ignored — not me ignoring my problems but make it syscall 💅

the aio_lio_opcode field of each aiocb specifies the operation to be performed. the supported operations are:

  • LIO_READ — read data as if by a call to aio_read(2).
  • LIO_READV — read data as if by a call to aio_readv(2).
  • LIO_NOP — no operation. literally nothing. a little rest moment 😌
  • LIO_WRITE — write data as if by a call to aio_write(2).
  • LIO_WRITEV — write data as if by a call to aio_writev(2).

if the LIO_READ, LIO_READV, LIO_WRITE, LIO_WRITEV opcodes are or-ed with the LIO_FOFFSET flag, the corresponding read or write operation uses the current file descriptor offset instead of aio_offset from aiocb. iykyk 🔥

if the mode argument is LIO_WAIT, lio_listio() does not return until all the requested operations have been completed. it's giving "i'm not leaving until this is done" ⏳ if mode is LIO_NOWAIT, sig can be used to request asynchronous notification when all operations have completed. if sig is NULL, no notification is sent. no thoughts, just silence 🙈

for SIGEV_KEVENT notifications, the posted kevent will contain:

  • ident — list
  • filter — EVFILT_LIO
  • udata — the value stored in sig->sigev_value

for SIGEV_SIGNO and SIGEV_THREAD_ID notifications, the information for the queued signal will include SI_ASYNCIO in the si_code field and the value stored in sig->sigev_value in the si_value field.

for SIGEV_THREAD notifications, the value stored in sig->sigev_value is passed to the sig->sigev_notify_function as described in sigevent(3).

the order in which the requests are carried out is not specified; in particular, there is no guarantee that they will be executed in the order 0, 1, ..., nent-1. so don't come for me about order, bestie — it's giving chaos and we're living for it 🌈

🎀 RETURN VALUES 🎀

  • if mode is LIO_WAIT: the lio_listio() function returns 0 if the operations completed successfully, otherwise -1.
  • if mode is LIO_NOWAIT: the lio_listio() function returns 0 if the operations are successfully queued, otherwise -1.

💀 ERRORS 💀

the lio_listio() function will fail if:

  • [EAGAIN] — there are not enough resources to enqueue the requests.
  • [EAGAIN] — the request would cause the system-wide limit {AIO_MAX} to be exceeded.
  • [EINVAL] — the mode argument is neither LIO_WAIT nor LIO_NOWAIT, or nent is greater than {AIO_LISTIO_MAX}.
  • [EINVAL] — the asynchronous notification method in sig->sigev_notify is invalid or not supported.
  • [EINTR] — a signal interrupted the system call before it could be completed.
  • [EIO] — one or more requests failed.

in addition, the lio_listio() function may fail for any of the reasons listed for aio_read(2) and aio_write(2).

bestie, important 🚨 if lio_listio() succeeds, or fails with an error code of EAGAIN, EINTR, or EIO, some of the requests may have been initiated. the caller should check the error status of each aiocb structure individually by calling aio_error(2). no cap — do the vibe check on every single one 💅

🫶 SEE ALSO 🫶

go read these, bestie — they're all part of the lore 📖✨

👑 STANDARDS 👑

the lio_listio() function is expected to conform to IEEE Std 1003.1-2001 (“POSIX.1”). the LIO_READV and LIO_WRITEV operations are FreeBSD extensions, and should not be used in portable code. so if you're writing portable code, leave those two at home, okay? they're giving FreeBSD exclusive and not invited to the cross-platform party 🚫💅

⭐ HISTORY ⭐

the lio_listio() system call first appeared in FreeBSD 3.0. a legend since day one, fr fr 🌟

that's the whole page, bestie 🫶 this one's from Debian, dated January 13, 2024, and it's the LIO_LISTIO(2) manual page — now go slay your I/O list 💅✨

📦 where this page comes from