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     aio_mlock — asynchronous mlock(2) operation


     Standard C Library (libc, -lc)


     #include <aio.h>

     aio_mlock(struct aiocb *iocb);


     The aio_mlock() system call allows the calling process to lock into memory the physical
     pages associated with the virtual address range starting at iocb->aio_buf for
     iocb->aio_nbytes bytes.  The call returns immediately after the locking request has been
     enqueued; the operation may or may not have completed at the time the call returns.

     The iocb pointer may be subsequently used as an argument to aio_return() and aio_error() in
     order to determine return or error status for the enqueued operation while it is in

     If the request could not be enqueued (generally due to aio(4) limits), then the call returns
     without having enqueued the request.


     The Asynchronous I/O Control Block structure pointed to by iocb and the buffer that the
     iocb->aio_buf member of that structure references must remain valid until the operation has
     completed.  For this reason, use of auto (stack) variables for these objects is discouraged.

     The asynchronous I/O control buffer iocb should be zeroed before the aio_mlock() call to
     avoid passing bogus context information to the kernel.

     Modifications of the Asynchronous I/O Control Block structure or the buffer contents after
     the request has been enqueued, but before the request has completed, are not allowed.


     The aio_mlock() function returns the value 0 if successful; otherwise the value -1 is
     returned and the global variable errno is set to indicate the error.


     The aio_mlock() system call will fail if:

     [EAGAIN]           The request was not queued because of system resource limitations.

     [ENOSYS]           The aio_mlock() system call is not supported.

     If the request is successfully enqueued, but subsequently cancelled or an error occurs, the
     value returned by the aio_return() system call is per the mlock(2) system call, and the
     value returned by the aio_error() system call is one of the error returns from the mlock(2)
     system call, or ECANCELED if the request was explicitly cancelled via a call to


     aio_cancel(2), aio_error(2), aio_return(2), mlock(2), aio(4)


     The aio_mlock() system call is a FreeBSD extension, and should not be used in portable code.


     The aio_mlock() system call first appeared in FreeBSD 10.0.


     The system call was introduced by Gleb Smirnoff <>.