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 } 85 close(e->wfd); 86 } 87 88 int event_notifier_get_fd(const EventNotifier *e) 89 { 90 return e->rfd; 91 } 92 93 int event_notifier_set(EventNotifier *e) 94 { 95 static const uint64_t value = 1; 96 ssize_t ret; 97 98 do { 99 ret = write(e->wfd, &value, sizeof(value)); 100 } while (ret < 0 && errno == EINTR); 101 102 /* EAGAIN is fine, a read must be pending. */ 103 if (ret < 0 && errno != EAGAIN) { 104 return -errno; 105 } 106 return 0; 107 } 108 109 int event_notifier_test_and_clear(EventNotifier *e) 110 { 111 int value; 112 ssize_t len; 113 char buffer[512]; 114 115 /* Drain the notify pipe. For eventfd, only 8 bytes will be read. */ 116 value = 0; 117 do { 118 len = read(e->rfd, buffer, sizeof(buffer)); 119 value |= (len > 0); 120 } while ((len == -1 && errno == EINTR) || len == sizeof(buffer)); 121 122 return value; 123 } 124