From 9c3060bedd84144653a2ad7bea32389f65598d40 Mon Sep 17 00:00:00 2001 From: Davide Libenzi Date: Thu, 10 May 2007 22:23:21 -0700 Subject: 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/aio.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include/linux/aio.h') diff --git a/include/linux/aio.h b/include/linux/aio.h index 43dc2ebfaa0e..b903fc02bdb7 100644 --- a/include/linux/aio.h +++ b/include/linux/aio.h @@ -119,6 +119,12 @@ struct kiocb { struct list_head ki_list; /* the aio core uses this * for cancellation */ + + /* + * If the aio_resfd field of the userspace iocb is not zero, + * this is the underlying file* to deliver event to. + */ + struct file *ki_eventfd; }; #define is_sync_kiocb(iocb) ((iocb)->ki_key == KIOCB_SYNC_KEY) -- cgit v1.2.3-58-ga151