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$FreeBSD: stable/10/share/man/man4/aio.4 321829 2017-07-31 22:36:03Z asomers $
.Dd June 22, 2017 .Dt AIO 4 .Os .Sh NAME .Nm aio .Nd asynchronous I/O .Sh SYNOPSIS To link into the kernel: .Cd "options VFS_AIO"
p To load as a kernel loadable module: .Dl kldload aio .Sh DESCRIPTION The .Nm facility provides system calls for asynchronous I/O. It is available both as a kernel option for static inclusion and as a dynamic kernel module.
p Asynchronous I/O control buffers should be zeroed before initializing individual fields. This ensures all fields are initialized.
p All asynchronous I/O control buffers contain a .Vt sigevent structure in the .Va aio_sigevent field which can be used to request notification when an operation completes.
p For .Dv SIGEV_KEVENT notifications, the .Va sigevent .Ap s .Va sigev_notify_kqueue field should contain the descriptor of the kqueue that the event should be attached to, its .Va sigev_notify_kevent_flags field may contain .Dv EV_ONESHOT , .Dv EV_CLEAR , and/or .Dv EV_DISPATCH , and its .Va sigev_notify field should be set to .Dv SIGEV_KEVENT . The posted kevent will contain: l -column ".Va filter" t Sy Member Ta Sy Value t Va ident Ta asynchronous I/O control buffer pointer t Va filter Ta Dv EVFILT_AIO t Va flags Ta Dv EV_EOF t Va udata Ta value stored in .Va aio_sigevent.sigev_value .El
p For .Dv SIGEV_SIGNO and .Dv SIGEV_THREAD_ID notifications, the information for the queued signal will include .Dv SI_ASYNCIO in the .Va si_code field and the value stored in .Va sigevent.sigev_value in the .Va si_value field.
p For .Dv SIGEV_THREAD notifications, the value stored in .Va aio_sigevent.sigev_value is passed to the .Va aio_sigevent.sigev_notify_function as described in .Xr sigevent 3 . .Sh SEE ALSO .Xr aio_cancel 2 , .Xr aio_error 2 , .Xr aio_read 2 , .Xr aio_return 2 , .Xr aio_suspend 2 , .Xr aio_waitcomplete 2 , .Xr aio_write 2 , .Xr lio_listio 2 , .Xr sigevent 3 , .Xr config 8 , .Xr kldload 8 , .Xr kldunload 8 .Sh HISTORY The .Nm facility appeared as a kernel option in .Fx 3.0 . The .Nm kernel module appeared in .Fx 5.0 .