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 (!g_unix_open_pipe(fds, FD_CLOEXEC, NULL)) { 53 return -errno; 54 } 55 if (!g_unix_set_fd_nonblocking(fds[0], true, NULL)) { 56 ret = -errno; 57 goto fail; 58 } 59 if (!g_unix_set_fd_nonblocking(fds[1], true, NULL)) { 60 ret = -errno; 61 goto fail; 62 } 63 e->rfd = fds[0]; 64 e->wfd = fds[1]; 65 } 66 e->initialized = true; 67 if (active) { 68 event_notifier_set(e); 69 } 70 return 0; 71 72 fail: 73 close(fds[0]); 74 close(fds[1]); 75 return ret; 76 } 77 78 void event_notifier_cleanup(EventNotifier *e) 79 { 80 if (!e->initialized) { 81 return; 82 } 83 84 if (e->rfd != e->wfd) { 85 close(e->rfd); 86 } 87 88 e->rfd = -1; 89 close(e->wfd); 90 e->wfd = -1; 91 e->initialized = false; 92 } 93 94 int event_notifier_get_fd(const EventNotifier *e) 95 { 96 return e->rfd; 97 } 98 99 int event_notifier_get_wfd(const EventNotifier *e) 100 { 101 return e->wfd; 102 } 103 104 int event_notifier_set(EventNotifier *e) 105 { 106 static const uint64_t value = 1; 107 ssize_t ret; 108 109 if (!e->initialized) { 110 return -1; 111 } 112 113 do { 114 ret = write(e->wfd, &value, sizeof(value)); 115 } while (ret < 0 && errno == EINTR); 116 117 /* EAGAIN is fine, a read must be pending. */ 118 if (ret < 0 && errno != EAGAIN) { 119 return -errno; 120 } 121 return 0; 122 } 123 124 int event_notifier_test_and_clear(EventNotifier *e) 125 { 126 int value; 127 ssize_t len; 128 char buffer[512]; 129 130 if (!e->initialized) { 131 return 0; 132 } 133 134 /* Drain the notify pipe. For eventfd, only 8 bytes will be read. */ 135 value = 0; 136 do { 137 len = read(e->rfd, buffer, sizeof(buffer)); 138 value |= (len > 0); 139 } while ((len == -1 && errno == EINTR) || len == sizeof(buffer)); 140 141 return value; 142 } 143