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 } 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 e->rfd = -1; 84 } 85 close(e->wfd); 86 e->wfd = -1; 87 } 88 89 int event_notifier_get_fd(const EventNotifier *e) 90 { 91 return e->rfd; 92 } 93 94 int event_notifier_set(EventNotifier *e) 95 { 96 static const uint64_t value = 1; 97 ssize_t ret; 98 99 do { 100 ret = write(e->wfd, &value, sizeof(value)); 101 } while (ret < 0 && errno == EINTR); 102 103 /* EAGAIN is fine, a read must be pending. */ 104 if (ret < 0 && errno != EAGAIN) { 105 return -errno; 106 } 107 return 0; 108 } 109 110 int event_notifier_test_and_clear(EventNotifier *e) 111 { 112 int value; 113 ssize_t len; 114 char buffer[512]; 115 116 /* Drain the notify pipe. For eventfd, only 8 bytes will be read. */ 117 value = 0; 118 do { 119 len = read(e->rfd, buffer, sizeof(buffer)); 120 value |= (len > 0); 121 } while ((len == -1 && errno == EINTR) || len == sizeof(buffer)); 122 123 return value; 124 } 125