1 /* 2 * event notifier support 3 * 4 * Copyright Red Hat, Inc. 2010 5 * 6 * Authors: 7 * Michael S. Tsirkin <mst@redhat.com> 8 * 9 * This work is licensed under the terms of the GNU GPL, version 2 or later. 10 * See the COPYING file in the top-level directory. 11 */ 12 13 #include "qemu/osdep.h" 14 #include "qemu/cutils.h" 15 #include "qemu/event_notifier.h" 16 #include "qemu/main-loop.h" 17 18 #ifdef CONFIG_EVENTFD 19 #include <sys/eventfd.h> 20 #endif 21 22 #ifdef CONFIG_EVENTFD 23 /* 24 * Initialize @e with existing file descriptor @fd. 25 * @fd must be a genuine eventfd object, emulation with pipe won't do. 26 */ 27 void event_notifier_init_fd(EventNotifier *e, int fd) 28 { 29 e->rfd = fd; 30 e->wfd = fd; 31 e->initialized = true; 32 } 33 #endif 34 35 int event_notifier_init(EventNotifier *e, int active) 36 { 37 int fds[2]; 38 int ret; 39 40 #ifdef CONFIG_EVENTFD 41 ret = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC); 42 #else 43 ret = -1; 44 errno = ENOSYS; 45 #endif 46 if (ret >= 0) { 47 e->rfd = e->wfd = ret; 48 } else { 49 if (errno != ENOSYS) { 50 return -errno; 51 } 52 if (qemu_pipe(fds) < 0) { 53 return -errno; 54 } 55 ret = fcntl_setfl(fds[0], O_NONBLOCK); 56 if (ret < 0) { 57 ret = -errno; 58 goto fail; 59 } 60 ret = fcntl_setfl(fds[1], O_NONBLOCK); 61 if (ret < 0) { 62 ret = -errno; 63 goto fail; 64 } 65 e->rfd = fds[0]; 66 e->wfd = fds[1]; 67 } 68 e->initialized = true; 69 if (active) { 70 event_notifier_set(e); 71 } 72 return 0; 73 74 fail: 75 close(fds[0]); 76 close(fds[1]); 77 return ret; 78 } 79 80 void event_notifier_cleanup(EventNotifier *e) 81 { 82 if (!e->initialized) { 83 return; 84 } 85 86 if (e->rfd != e->wfd) { 87 close(e->rfd); 88 } 89 90 e->rfd = -1; 91 close(e->wfd); 92 e->wfd = -1; 93 e->initialized = false; 94 } 95 96 int event_notifier_get_fd(const EventNotifier *e) 97 { 98 return e->rfd; 99 } 100 101 int event_notifier_get_wfd(const EventNotifier *e) 102 { 103 return e->wfd; 104 } 105 106 int event_notifier_set(EventNotifier *e) 107 { 108 static const uint64_t value = 1; 109 ssize_t ret; 110 111 if (!e->initialized) { 112 return -1; 113 } 114 115 do { 116 ret = write(e->wfd, &value, sizeof(value)); 117 } while (ret < 0 && errno == EINTR); 118 119 /* EAGAIN is fine, a read must be pending. */ 120 if (ret < 0 && errno != EAGAIN) { 121 return -errno; 122 } 123 return 0; 124 } 125 126 int event_notifier_test_and_clear(EventNotifier *e) 127 { 128 int value; 129 ssize_t len; 130 char buffer[512]; 131 132 if (!e->initialized) { 133 return 0; 134 } 135 136 /* Drain the notify pipe. For eventfd, only 8 bytes will be read. */ 137 value = 0; 138 do { 139 len = read(e->rfd, buffer, sizeof(buffer)); 140 value |= (len > 0); 141 } while ((len == -1 && errno == EINTR) || len == sizeof(buffer)); 142 143 return value; 144 } 145