2292b33986
event notifiers are slightly generalized eventfd descriptors. Current implementation depends on eventfd because vhost is the only user, and vhost depends on eventfd anyway, but a stub is provided for non-eventfd case. We'll be able to further generalize this when another user comes along and we see how to best do this. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
63 lines
1.3 KiB
C
63 lines
1.3 KiB
C
/*
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* event notifier support
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*
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* Copyright Red Hat, Inc. 2010
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*
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* Authors:
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* Michael S. Tsirkin <mst@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*/
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#include "hw.h"
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#include "event_notifier.h"
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#ifdef CONFIG_EVENTFD
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#include <sys/eventfd.h>
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#endif
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int event_notifier_init(EventNotifier *e, int active)
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{
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#ifdef CONFIG_EVENTFD
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int fd = eventfd(!!active, EFD_NONBLOCK | EFD_CLOEXEC);
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if (fd < 0)
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return -errno;
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e->fd = fd;
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return 0;
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#else
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return -ENOSYS;
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#endif
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}
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void event_notifier_cleanup(EventNotifier *e)
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{
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close(e->fd);
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}
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int event_notifier_get_fd(EventNotifier *e)
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{
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return e->fd;
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}
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int event_notifier_test_and_clear(EventNotifier *e)
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{
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uint64_t value;
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int r = read(e->fd, &value, sizeof(value));
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return r == sizeof(value);
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}
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int event_notifier_test(EventNotifier *e)
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{
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uint64_t value;
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int r = read(e->fd, &value, sizeof(value));
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if (r == sizeof(value)) {
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/* restore previous value. */
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int s = write(e->fd, &value, sizeof(value));
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/* never blocks because we use EFD_SEMAPHORE.
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* If we didn't we'd get EAGAIN on overflow
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* and we'd have to write code to ignore it. */
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assert(s == sizeof(value));
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}
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return r == sizeof(value);
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}
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