2ec10b952b
EventNotifier right now cannot be used as an inter-thread communication primitive. It only works if something else (the kernel) sets the eventfd. Add a primitive to signal an EventNotifier that another thread is waiting on. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com>
69 lines
1.5 KiB
C
69 lines
1.5 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 or later.
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* See the COPYING file in the top-level directory.
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*/
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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_set(EventNotifier *e)
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{
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uint64_t value = 1;
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int r = write(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_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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