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/cutils.h" 16 #include "qemu/event_notifier.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 e->cleanup = NULL; 33 } 34 #endif 35 36 int event_notifier_init(EventNotifier *e, int active) 37 { 38 int fds[2]; 39 int ret; 40 41 #ifdef CONFIG_EVENTFD 42 ret = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC); 43 #else 44 ret = -1; 45 errno = ENOSYS; 46 #endif 47 if (ret >= 0) { 48 e->rfd = e->wfd = ret; 49 } else { 50 if (errno != ENOSYS) { 51 return -errno; 52 } 53 if (qemu_pipe(fds) < 0) { 54 return -errno; 55 } 56 ret = fcntl_setfl(fds[0], O_NONBLOCK); 57 if (ret < 0) { 58 ret = -errno; 59 goto fail; 60 } 61 ret = fcntl_setfl(fds[1], O_NONBLOCK); 62 if (ret < 0) { 63 ret = -errno; 64 goto fail; 65 } 66 e->rfd = fds[0]; 67 e->wfd = fds[1]; 68 } 69 e->cleanup = NULL; 70 if (active) { 71 event_notifier_set(e); 72 } 73 return 0; 74 75 fail: 76 close(fds[0]); 77 close(fds[1]); 78 return ret; 79 } 80 81 void event_notifier_cleanup(EventNotifier *e) 82 { 83 if (e->rfd != e->wfd) { 84 close(e->rfd); 85 } 86 close(e->wfd); 87 e->rfd = -1; 88 e->wfd = -1; 89 e->cleanup = NULL; 90 } 91 92 int event_notifier_get_fd(const EventNotifier *e) 93 { 94 return e->rfd; 95 } 96 97 int event_notifier_set(EventNotifier *e) 98 { 99 static const uint64_t value = 1; 100 ssize_t ret; 101 102 do { 103 ret = write(e->wfd, &value, sizeof(value)); 104 } while (ret < 0 && errno == EINTR); 105 106 /* EAGAIN is fine, a read must be pending. */ 107 if (ret < 0 && errno != EAGAIN) { 108 return -errno; 109 } 110 return 0; 111 } 112 113 int event_notifier_test_and_clear(EventNotifier *e) 114 { 115 int value; 116 ssize_t len; 117 char buffer[512]; 118 119 /* Drain the notify pipe. For eventfd, only 8 bytes will be read. */ 120 value = 0; 121 do { 122 len = read(e->rfd, buffer, sizeof(buffer)); 123 value |= (len > 0); 124 } while ((len == -1 && errno == EINTR) || len == sizeof(buffer)); 125 126 return value; 127 } 128