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The io_uring file descriptor monitoring implementation has an internal
list of fd handlers that are pending submission to io_uring.
fdmon_io_uring_destroy() deletes all fd handlers on the list.
Don't delete fd handlers directly in fdmon_io_uring_destroy() for two
reasons:
1. This duplicates the aio-posix.c AioHandler deletion code and could
become outdated if the struct changes.
2. Only handlers with the FDMON_IO_URING_REMOVE flag set are safe to
remove. If the flag is not set then something still has a pointer to
the fd handler. Let aio-posix.c and its user worry about that. In
practice this isn't an issue because fdmon_io_uring_destroy() is only
called when shutting down so all users have removed their fd
handlers, but the next patch will need this!
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-by: Oleksandr Natalenko <oleksandr@redhat.com>
Message-id: 20200511183630.279750-2-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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The io_uring_enter(2) syscall returns with errno=EINTR when interrupted
by a signal. Retry the syscall in this case.
It's essential to do this in the io_uring_submit_and_wait() case. My
interpretation of the Linux v5.5 io_uring_enter(2) code is that it
shouldn't affect the io_uring_submit() case, but there is no guarantee
this will always be the case. Let's check for -EINTR around both APIs.
Note that the liburing APIs have -errno return values.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20200408091139.273851-1-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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When a file descriptor becomes ready we must re-arm POLL_ADD. This is
done by adding an sqe to the io_uring sq ring. The ->need_wait()
function wasn't taking pending sqes into account and therefore
io_uring_submit_and_wait() was not being called. Polling for cqes
failed to detect fd readiness since we hadn't submitted the sqe to
io_uring.
This patch fixes the following tests/test-aio -p /aio/event/wait
failure:
ok 11 /aio/event/wait
**
ERROR:tests/test-aio.c:374:test_flush_event_notifier: assertion failed: (aio_poll(ctx, false))
Reported-by: Cole Robinson <crobinso@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Tested-by: Cole Robinson <crobinso@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20200402145434.99349-1-stefanha@redhat.com
Fixes: 73fd282e7b6dd4e4ea1c3bbb3d302c8db51e4ccf
("aio-posix: add io_uring fd monitoring implementation")
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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When external event sources are disabled fdmon-io_uring falls back to
fdmon-poll. The ->need_wait() callback needs to watch for this so it
can return true when external event sources are disabled.
It is also necessary to call ->wait() when AioHandlers have changed
because io_uring is asynchronous and we must submit new sqes.
Both of these changes to ->need_wait() together fix tests/test-aio -p
/aio/external-client, which failed with:
test-aio: tests/test-aio.c:404: test_aio_external_client: Assertion `aio_poll(ctx, false)' failed.
Reported-by: Julia Suvorova <jusual@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20200319163559.117903-1-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Unlike ppoll(2) and epoll(7), Linux io_uring completions can be polled
from userspace. Previously userspace polling was only allowed when all
AioHandler's had an ->io_poll() callback. This prevented starvation of
fds by userspace pollable handlers.
Add the FDMonOps->need_wait() callback that enables userspace polling
even when some AioHandlers lack ->io_poll().
For example, it's now possible to do userspace polling when a TCP/IP
socket is monitored thanks to Linux io_uring.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Link: https://lore.kernel.org/r/20200305170806.1313245-7-stefanha@redhat.com
Message-Id: <20200305170806.1313245-7-stefanha@redhat.com>
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The recent Linux io_uring API has several advantages over ppoll(2) and
epoll(2). Details are given in the source code.
Add an io_uring implementation and make it the default on Linux.
Performance is the same as with epoll(7) but later patches add
optimizations that take advantage of io_uring.
It is necessary to change how aio_set_fd_handler() deals with deleting
AioHandlers since removing monitored file descriptors is asynchronous in
io_uring. fdmon_io_uring_remove() marks the AioHandler deleted and
aio_set_fd_handler() will let it handle deletion in that case.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Link: https://lore.kernel.org/r/20200305170806.1313245-6-stefanha@redhat.com
Message-Id: <20200305170806.1313245-6-stefanha@redhat.com>
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