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author | Davide Libenzi <davidel@xmailserver.org> | 2007-05-11 09:23:21 +0400 |
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committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-05-11 19:29:37 +0400 |
commit | 9c3060bedd84144653a2ad7bea32389f65598d40 (patch) | |
tree | 80336eb24be8458cda1f35ee752f05bc7c329fbb /include/linux/aio_abi.h | |
parent | fdb902b1225e1668315f38e96d2f439452c03a15 (diff) | |
download | linux-9c3060bedd84144653a2ad7bea32389f65598d40.tar.xz |
signal/timer/event: KAIO eventfd support example
This is an example about how to add eventfd support to the current KAIO code,
in order to enable KAIO to post readiness events to a pollable fd (hence
compatible with POSIX select/poll). The KAIO code simply signals the eventfd
fd when events are ready, and this triggers a POLLIN in the fd. This patch
uses a reserved for future use member of the struct iocb to pass an eventfd
file descriptor, that KAIO will use to post events every time a request
completes. At that point, an aio_getevents() will return the completed result
to a struct io_event. I made a quick test program to verify the patch, and it
runs fine here:
http://www.xmailserver.org/eventfd-aio-test.c
The test program uses poll(2), but it'd, of course, work with select and epoll
too.
This can allow to schedule both block I/O and other poll-able devices
requests, and wait for results using select/poll/epoll. In a typical
scenario, an application would submit KAIO request using aio_submit(), and
will also use epoll_ctl() on the whole other class of devices (that with the
addition of signals, timers and user events, now it's pretty much complete),
and then would:
epoll_wait(...);
for_each_event {
if (curr_event_is_kaiofd) {
aio_getevents();
dispatch_aio_events();
} else {
dispatch_epoll_event();
}
}
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/aio_abi.h')
-rw-r--r-- | include/linux/aio_abi.h | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/include/linux/aio_abi.h b/include/linux/aio_abi.h index e3ca0a485cc6..9e0172931315 100644 --- a/include/linux/aio_abi.h +++ b/include/linux/aio_abi.h @@ -45,6 +45,14 @@ enum { IOCB_CMD_PWRITEV = 8, }; +/* + * Valid flags for the "aio_flags" member of the "struct iocb". + * + * IOCB_FLAG_RESFD - Set if the "aio_resfd" member of the "struct iocb" + * is valid. + */ +#define IOCB_FLAG_RESFD (1 << 0) + /* read() from /dev/aio returns these structures. */ struct io_event { __u64 data; /* the data field from the iocb */ @@ -84,7 +92,15 @@ struct iocb { /* extra parameters */ __u64 aio_reserved2; /* TODO: use this for a (struct sigevent *) */ - __u64 aio_reserved3; + + /* flags for the "struct iocb" */ + __u32 aio_flags; + + /* + * if the IOCB_FLAG_RESFD flag of "aio_flags" is set, this is an + * eventfd to signal AIO readiness to + */ + __u32 aio_resfd; }; /* 64 bytes */ #undef IFBIG |