- Avoid double use of "request" in a single sentence. Instead, describe
aio_sigevent as being used to request notification of the associated
operation's completion. This matches the language used to describe
aio_sigevent in aio(4).
- Simplify the prohibition on modifying buffers while requests are in
flight.
- Fix case mismatch.
- Drop note about not using stack variables. C programmers should be able
to figure out if a stack variable is safe based on the later warning
about the life cycle requirements of control blocks.
- Remove prohibition on modifying the I/O buffer for aio_fsync() since
it does not use an I/O buffer. For aio_mlock(), prohibit modifications
to the mapping (e.g. due to mprotect, munmap, mmap, etc.) but do not
prohibit modifications to the memory backing the buffer (stores into
the pages backing the buffer).
Requested by: wblock (1,2), kib (4)
Reviewed by: kib, rpokala, wblock
MFC after: 3 days
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D7462
The asynchronous I/O changes made previously result in different
behavior out of the box. Previously all AIO requests failed with
ENOSYS / SIGSYS unless aio.ko was explicitly loaded. Now, some AIO
requests complete and others ("unsafe" requests) fail with EOPNOTSUPP.
Reword the introductory paragraph in aio(4) to add a general
description of AIO before describing the vfs.aio.enable_unsafe sysctl.
Remove the ENOSYS error description from aio_fsync(2), aio_read(2),
and aio_write(2) and replace it with a description of EOPNOTSUPP.
Remove the ENOSYS error description from aio_mlock(2).
Log a message to the system log the first time a process requests an
"unsafe" AIO request that fails with EOPNOTSUPP. This is modeled on
the log message used for processes using the legacy pty devices.
Reviewed by: kib (earlier version)
MFC after: 1 week
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D7151
- Add a sigevent(3) manpage to give a general overview of the sigevent
structure and the available notification mechanisms.
- Document that AIO requests contain a nested sigevent structure that can
be used to request completion notification.
- Expand the sigevent details in other manuals to note details such as
the extra values stored in a queued signal's information or in a posted
kevent.
Reviewed by: kib
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D7122
