Module Name: src
Committed By: jruoho
Date: Wed May 19 06:35:20 UTC 2010
Modified Files:
src/lib/librt: aio.3
Log Message:
Remove the paragraph about the used notification mechanism. Instead,
reference sigevent(3). Clarify the file offset discussion.
To generate a diff of this commit:
cvs rdiff -u -r1.4 -r1.5 src/lib/librt/aio.3
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/lib/librt/aio.3
diff -u src/lib/librt/aio.3:1.4 src/lib/librt/aio.3:1.5
--- src/lib/librt/aio.3:1.4 Mon May 17 19:22:31 2010
+++ src/lib/librt/aio.3 Wed May 19 06:35:20 2010
@@ -1,4 +1,4 @@
-.\" $NetBSD: aio.3,v 1.4 2010/05/17 19:22:31 jruoho Exp $ $
+.\" $NetBSD: aio.3,v 1.5 2010/05/19 06:35:20 jruoho Exp $ $
.\"
.\" Copyright (c) 2010 Jukka Ruohonen <[email protected]>
.\" All rights reserved.
@@ -24,7 +24,7 @@
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
-.Dd May 17, 2010
+.Dd May 19, 2010
.Dt AIO 3
.Os
.Sh NAME
@@ -184,10 +184,21 @@
operations are not strictly sequential;
operations are carried out in arbitrary order and more than one
operation for one file descriptor can be started.
-Each operation must specify an offset, but the actual file offset
-is never updated as a result of an
+The requested read or write operation starts
+from the absolute position specified by
+.Va aio_offset ,
+as if
+.Xr lseek 2
+would have been called with
+.Dv SEEK_SET
+immediately prior to the operation.
+The
+.Tn POSIX
+standard does not specify what happens after an
.Nm
-operation.
+operation has been successfully completed.
+Depending on the implementation,
+the actual file offset may or may not be updated.
.Ss Errors and Completion
Asynchronous
.Tn I/O
@@ -244,37 +255,8 @@
The notification model is implemented by using the
.Va aio_sigevent
member of the Asynchronous I/O Control Block.
-The structure
-.Em sigevent
-is defined in
-.In signal.h .
-The relevant fields for
-.Nm
-are
-.Va sigev_notify ,
-.Va sigev_signo ,
-and the function pointer
-.Va sigev_notify_function .
-The
-.Va sigev_notify
-member determines the type of the action:
-.Bl -enum -offset indent
-.It
-If it is
-.Dv SIGEV_NONE ,
-no notification is sent.
-.It
-If it is
-.Dv SIGEV_SIGNAL ,
-the signal determined by
-.Va sigev_signo
-is sent when the operation completes.
-.It
-If it is
-.Dv SIGEV_THREAD ,
-a thread is created which starts executing the function specified by
-.Va sigev_notify_function .
-.El
+The operational model and the used structure are described in
+.Xr sigevent 3 .
.Pp
The
.Fn aio_suspend
@@ -351,9 +333,16 @@
interface first appeared in
.Nx 5.0 .
.Sh CAVEATS
+Few limitations can be mentioned:
+.Bl -bullet
+.It
+Undefined behavior results if simultaneous asynchronous operations
+use the same Asynchronous I/O Control Block.
+.It
When an asynchronous read operation is outstanding,
undefined behavior may follow if the contents of
.Va aiocb
are altered, or if memory associated with the structure, or the
.Va aio_buf
buffer, is deallocated.
+.El
