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 "sysemu/char.h" 18 #include "qemu/main-loop.h" 19 20 #ifdef CONFIG_EVENTFD 21 #include <sys/eventfd.h> 22 #endif 23 24 #ifdef CONFIG_EVENTFD 25 /* 26 * Initialize @e with existing file descriptor @fd. 27 * @fd must be a genuine eventfd object, emulation with pipe won't do. 28 */ 29 void event_notifier_init_fd(EventNotifier *e, int fd) 30 { 31 e->rfd = fd; 32 e->wfd = fd; 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 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->rfd != e->wfd) { 83 close(e->rfd); 84 e->rfd = -1; 85 } 86 close(e->wfd); 87 e->wfd = -1; 88 } 89 90 int event_notifier_get_fd(const EventNotifier *e) 91 { 92 return e->rfd; 93 } 94 95 int event_notifier_set(EventNotifier *e) 96 { 97 static const uint64_t value = 1; 98 ssize_t ret; 99 100 do { 101 ret = write(e->wfd, &value, sizeof(value)); 102 } while (ret < 0 && errno == EINTR); 103 104 /* EAGAIN is fine, a read must be pending. */ 105 if (ret < 0 && errno != EAGAIN) { 106 return -errno; 107 } 108 return 0; 109 } 110 111 int event_notifier_test_and_clear(EventNotifier *e) 112 { 113 int value; 114 ssize_t len; 115 char buffer[512]; 116 117 /* Drain the notify pipe. For eventfd, only 8 bytes will be read. */ 118 value = 0; 119 do { 120 len = read(e->rfd, buffer, sizeof(buffer)); 121 value |= (len > 0); 122 } while ((len == -1 && errno == EINTR) || len == sizeof(buffer)); 123 124 return value; 125 } 126