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-common.h" 15 #include "qemu/event_notifier.h" 16 #include "sysemu/char.h" 17 #include "qemu/main-loop.h" 18 19 #ifdef CONFIG_EVENTFD 20 #include <sys/eventfd.h> 21 #endif 22 23 #ifdef CONFIG_EVENTFD 24 /* 25 * Initialize @e with existing file descriptor @fd. 26 * @fd must be a genuine eventfd object, emulation with pipe won't do. 27 */ 28 void event_notifier_init_fd(EventNotifier *e, int fd) 29 { 30 e->rfd = fd; 31 e->wfd = fd; 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 if (active) { 69 event_notifier_set(e); 70 } 71 return 0; 72 73 fail: 74 close(fds[0]); 75 close(fds[1]); 76 return ret; 77 } 78 79 void event_notifier_cleanup(EventNotifier *e) 80 { 81 if (e->rfd != e->wfd) { 82 close(e->rfd); 83 } 84 close(e->wfd); 85 } 86 87 int event_notifier_get_fd(const EventNotifier *e) 88 { 89 return e->rfd; 90 } 91 92 int event_notifier_set_handler(EventNotifier *e, 93 EventNotifierHandler *handler) 94 { 95 qemu_set_fd_handler(e->rfd, (IOHandler *)handler, NULL, e); 96 return 0; 97 } 98 99 int event_notifier_set(EventNotifier *e) 100 { 101 static const uint64_t value = 1; 102 ssize_t ret; 103 104 do { 105 ret = write(e->wfd, &value, sizeof(value)); 106 } while (ret < 0 && errno == EINTR); 107 108 /* EAGAIN is fine, a read must be pending. */ 109 if (ret < 0 && errno != EAGAIN) { 110 return -errno; 111 } 112 return 0; 113 } 114 115 int event_notifier_test_and_clear(EventNotifier *e) 116 { 117 int value; 118 ssize_t len; 119 char buffer[512]; 120 121 /* Drain the notify pipe. For eventfd, only 8 bytes will be read. */ 122 value = 0; 123 do { 124 len = read(e->rfd, buffer, sizeof(buffer)); 125 value |= (len > 0); 126 } while ((len == -1 && errno == EINTR) || len == sizeof(buffer)); 127 128 return value; 129 } 130