Thomas Sailer wrote:
>
> johan verrept wrote:
>
> > If you have reasons not to do this, please let me know.
>
> Do you know what the AIO code does? I would prefer to do the same
> as the AIO code, because that will be the least surprise solution...
The parts of the code I have found that sends siginfo SIGIO, in fs/fcntl.c
(__kill_fasync()) and
fs/dnotify.c (__inode_dir_notify()) retrieve the f_own struct from the file * (which
is set by
F_SETOWN).
The manpage of fcntl, especially the description of F_SETOWN and F_SETSIG, seems to
point to what I
suggest. Following manpages seems to be the way of the least surprise?
man pages fcntl(2) qouted below.
J.
F_SETOWN
Set the process ID or process group that will
receive SIGIO and SIGURG signals for events on file
descriptor fd. Process groups are specified using
negative values. (F_SETSIG can be used to specify
a different signal instead of SIGIO).
If you set the O_ASYNC status flag on a file
descriptor (either by providing this flag with the
open(2) call, or by using the F_SETFL command of
fcntl), a SIGIO signal is sent whenever input or
output becomes possible on that file descriptor.
The process or process group to receive the signal
can be selected by using the F_SETOWN command to
the fcntl function. If the file descriptor is a
socket, this also selects the recipient of SIGURG
signals that are delivered when out-of-band data
arrives on that socket. (SIGURG is sent in any
situation where select(2) would report the socket
as having an "exceptional condition".) If the file
descriptor corresponds to a terminal device, then
SIGIO signals are sent to the foreground process
group of the terminal.
F_SETSIG
Sets the signal sent when input or output becomes
possible. A value of zero means to send the
default SIGIO signal. Any other value (including
SIGIO) is the signal to send instead, and in this
case additional info is available to the signal
handler if installed with SA_SIGINFO.
By using F_SETSIG with a non-zero value, and set
ting SA_SIGINFO for the signal handler (see sigac
tion(2)), extra information about I/O events is
passed to the handler in a siginfo_t structure. If
the si_code field indicates the source is SI_SIGIO,
the si_fd field gives the file descriptor associ
ated with the event. Otherwise, there is no indi
cation which file descriptors are pending, and you
should use the usual mechanisms (select(2),
poll(2), read(2) with O_NONBLOCK set etc.) to
determine which file descriptors are available for
I/O.
By selecting a POSIX.1b real time signal (value >=
SIGRTMIN), multiple I/O events may be queued using
the same signal numbers. (Queuing is dependent on
available memory). Extra information is available
if SA_SIGINFO is set for the signal handler, as
above.
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