Error handling
The Asynchronous I/O feature handles errors by returning
a value of -1 and placing an error number in the externally
declared variable errno.
It is included in <errno.h>.
The value of errno or the
aio_error function can be set to one of the following:
EAGAIN-
The requested Asynchronous I/O operation was not queued
because of system resource limitations.
The first request to encounter a resource limitation and all later
requests will be marked such that aio_error returns
EAGAIN.
EFAULT-
aiocbp or the aio_buf
member points outside the allocated address space.
ECANCELED-
The requested I/O was canceled before the I/O completed
because of an explicit aio_cancel request.
EINVAL-
All requests are NULL
or have their lio_listio set to
LIO_NOP.
This is used for lio_listio only.
EINVAL-
nent is zero.
This is used for lio_listio only.
EINVAL-
On SVR4.2, the request does not have the
AIO_RAW
flag bit set in aio_flags.
EFAULT-
A memory fault occurred while accessing a lio_listio request.
In this cause, lio_listio returns immediately without processing
later requests in the list.
On some implementations, memory faults might result in a SIGSEGV
signal being delivered to the processes instead of returning the
error code.
This is used for lio_listio only.
Error behavior
The following describes the detailed error behavior for
the lio_listio and aio_cancel functions.
lio_listio-
If the number of entries indicated by nent
causes the system-wide
limit AIO_MAX to be exceeded, lio_listio
returns with -1 and sets errno to EAGAIN after
marking EAGAIN in all requests.
If nent is greater than AIO_LISTIO_MAX,
lio_listio returns immediately
with -1 and sets errno to EINVAL.
No requests are processed or touched.
Requests are processed as follows:
-
If there is a memory fault while accessing a request,
lio_listio immediately returns -1 or EFAULT,
or causes a SIGSEGV.
-
If a resource problem occurs while queuing
a request, lio_listio returns -1
and sets errno to EAGAIN for all remaining requests.
-
If any other problem occurs with
a request, lio_listio returns -1
and sets errno to the appropriate error code.
lio_listio continues processing requests
and remembers what was wrong with the request in order
for lio_listio to return this error code.
The callback or signal will not be executed for that request.
Note that if different errors occur while processing
requests, it is unspecified which error code gets returned.
For example, it could be the first error encountered, or the last one.
-
If all requests from 1 through nent
have aio_lio_opcode = LIO_NOP or nent
is zero, lio_listio returns -1 or EINVAL.
aio_cancel-
aio_cancel returns AIO_CANCELED if all requests were
either canceled or completed and at least one request was canceled.
If an attempt was made to cancel a request that is in progress,
but it is uncertain whether the request will be canceled,
aio_cancel will return AIO_NOTCANCELED.
Next topic:
Using the interface functions
Previous topic:
Using the asynchronous I/O memory lock
© 2004 The SCO Group, Inc. All rights reserved.
UnixWare 7 Release 7.1.4 - 27 April 2004